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PARASITES.

PARASITES;

A TREATISE ON THE

ENTOZOA OF MAN AND ANIMALS,

INCLUDING

SOME ACCOUNT OF THE ECTOZOA.

BY

T. SPENCER COBBOLD, M.D., F.R.S., F.L.S.,

HONORARY VICE-PRESIDENT OF THE BIRMINGHAM NATURAL HISTORY
AND MICROSCOPICAL SOCIETY.

LONDON:
J. & A. CHURCHILL, NEW BURLINGTON STREET.
1879.

PREFACE

My introductory treatise on the Entozoa having long been out of print, it occurred to me that instead of attempting another edition it would be better to write an entirely new work, employing only such fragmentary portions of the old treatise as would harmonise with the far wider design I have now in view. Whilst, therefore, I have freely utilised a selection of the illustrations given in the elementary volume, comparatively few of its pages have been incorporated in the present work.

Dealing with parasites and parasitism after a manner not hitherto attempted I have purposely omitted minute anatomical descriptions, and, with rare exceptions, I have avoided the introduction of clinical details. While bringing to a focus the records of, and principal references to, a widely scattered, intricate, and voluminous literature, it has been my chief endeavour to supply abundance of original matter of a kind that cannot be found in the columns of any existing treatise. Whether I have succeeded or not the experienced helminthologist alone can judge. He, at all events, will perceive that the summary, though compressed within the space of a moderate-sized octavo, can only have resulted from sustained effort.

This treatise is not professional, that is to say, it does not concern itself with therapeutics or the curative treatment of parasitic affections; yet it introduces and helps to solve many questions relating to epidemics, endemics, and epizoötics due to parasites. The medical man who only looks at the phenomena of parasitism as displayed within the human territory must of necessity acquire a cramped, narrow, and distorted conception of the rôle played by parasites in the production of disease. Let it be freely granted that to the practising physician, as such, it matters little how many beasts, birds, reptiles, or fishes perish annually from parasitic affections; yet, when it is demonstrable that a large proportion of the strictly human entozoa require a change of hosts—or, in other words, need to pass through the bodies of the lower animals—then it is evident that some acquaintance on his part with the entozoa infesting animals becomes a practical necessity. Knowledge of the kind here offered will often materially aid him in recommending prophylactic measures. Moreover, the study of comparative pathology, almost ignored in England, conveys with it other lessons of high value in relation to the healing art. The great mind of John Hunter comprehended all this long ago, as any student of the beautiful preparations contained in the museum of the Royal College of Surgeons may readily convince himself; and this is all the more noteworthy, since the subject concerns the physician rather than the surgeon.

To the naturalist the second half of this book addresses itself in a very direct manner. When engaged in his dissections, an appeal to its pages will often enable him to decide at once as to the species of parasite accidentally encountered, and if a full diagnosis be demanded it will guide him to better sources of information. Many hundreds of correspondents, not having ready access to the systematic writings of Rudolphi, Diesing, and Dujardin, have requested me to identify their “finds.” I have rarely or never failed to comply with their requests; but it is hoped that the present work may prove of ready service to subsequent inquirers, and thus place a reasonable limit upon the number of future applicants. Since the manuscript of this work was completed I have received Dr von Linstow’s Compendium der Helminthologie, which, for the purposes held in view by the author, leaves little to be desired.

Expressly to meet the requirements of the Sanitarian I have dwelt upon the developmental phenomena exhibited by those parasites that occasion fatal helminthiases; and, in this relation, I have not confined my remarks to the parasites that are injurious to man in a direct manner, but have extended my observations to the genesis of those entozoa that prove destructive to horses, to beasts of burden generally, and to other creatures which, like cats and dogs, are in various ways subservient to man’s wants. It will be seen that in this way several questions relating to the purity of water and flesh-food, respectively, have been incidentally brought under notice.

In view of the magnitude of the task which my enthusiasm, perhaps unwarrantable, has led me to undertake, I know full well how considerately my foreign friends and correspondents will deal with the errors of omission and commission that they will certainly detect in these pages. If there be any educated persons at home who still affect to despise the revelations of helminthology, I can assure them that their prejudices are misplaced. The study of the structure and economy of a humble parasite brings to the investigator no slight insight into the workings of nature. If these workings cannot at all times be pronounced to be “good and beautiful,” they must at least be characterised as “true.” The knowledge of the true—especially if that knowledge by its practical applications be calculated to confer substantial benefits upon man and his inferior fellow-creatures—ought to be held in high esteem; but, apart from this purely utilitarian view, there remains for the investigator the delight occasioned by the in-rush of new scientific ideas. The average mind, being either essentially commercial or ridiculously sentimental, as the case may be, is totally incapable of comprehending the motive power that animates and guides the votary of science. The late Professor Faraday, a man wholly untinged by the ambitions of wealth and power, once remarked to me that there were no people so difficult to instruct as those who were ignorant of their own ignorance. It is just these very persons who, when placed in high positions of social, political, or professional trust, most powerfully contribute to check a nation’s progress. There are too few genuine workers at science in this country. As one of the rank and file, I claim only to have honestly contributed my mite. I should like to see a small army of helminthologists rise up and lay siege to the fortresses at present securely held by thousands of death-dealing parasites.

T. S. C.

74, Portsdown Road, London
May, 1879.

SYNOPSIS OF CONTENTS.

LIST OF BIBLIOGRAPHIES.

ERRATUM.

Page [296], line 24 from the top, for “in the glow-worm (Glomeris),” read “in a myriapod (Glomeris) which is phosphorescent like the glow-worm.”

PARASITES.

INTRODUCTION.

No person can derive advantage from the study of parasites unless the subject be approached in a right frame of mind. In other words, the student of helminthology must, as a primary discipline, dispossess himself of all preconceived opinions whatsoever, and in an attitude of child-like simplicity seek truth for its own sake. Unless the mind be absolutely free and unfettered it cannot rightly interpret the facts of this peculiar department of biological science. Those students who are nervously anxious to reconcile the conclusions of modern science with the ideas of their forefathers are certain to remain just as ignorant of the true value and significance of nature-teachings as all their fathers were.

Whether dealing with the external or internal forms, the study of parasites of man and animals is practically one of boundless extent; and there is probably no department of knowledge, possessing an equal value in relation to the welfare of man and beast, that is so thoroughly misunderstood by those who are directly concerned in the appreciation of its revelations. This has arisen from a total misconception as to cause and effect. Most people, not excluding even the votaries of the healing art, following tradition, regard the internal parasites or entozoa as creatures either directly resulting from certain diseased conditions of their hosts or as organisms which would not have existed if their bearers had been perfectly healthy. Nothing can be more absurd. Such a conclusion is utterly at variance with all logical deduction from known facts. It is, however, quite on a par with multitudes of other popular delusions which, in spite of the advance of science, will probably never become wholly eradicated from the public mind. People who hold these notions either cannot or do not desire to reject a view which has for them a dominating power almost equal to that of any known religious dogma. In conversation I have repeatedly noticed this to be the case. These people are the victims of educated ignorance and they will never allow that parasites are natural developments, accomplishing ends or parts of the orderly mystery which reigns everywhere. Some of then still cling to the creed that the presence of parasites, of internal ones at least, betokens evidence of Divine disfavor; and their minds are troubled with all sorts of distressing and childish conceptions. In the present age one would have thought that such ridiculous ideas could not be seriously maintained; but instead of being relegated to the limbo of similar “old wives’ fables” they dominate the opinions of thousands of our so-called educated people. The genuine searcher after truth does not need to be told that all preconceptions of this order hopelessly obscure the mental vision. They operate to render a just and adequate understanding of the science of helminthology impossible. The biologist may say what he lists, but he knows perfectly well that the superstitious mind will continue to ignore the precious and elevating results of scientific research, and that it will perseveringly continue to persuade itself that internal worms, parasites, and entozoa, of whatever kind, belong to the category of “plagues” liable to be distributed as special punishments for human wrong-doing.

As remarked in my previous treatise, the best way of studying the entozoa is to regard them as collectively forming a peculiar fauna, destined to occupy an equally peculiar territory. That territory is the wide-spread domain of the interior of the bodies of man and animals. Each bearer or “host” may be viewed as a continent, and each part or viscus of his body may be regarded as a district. Each district has its special attractions for particular parasitic forms; yet, at the same time, neither the district nor the continent are suitable as permanent resting-places for the invader. None of the internal parasites “continue in one stay;” all have a tendency to roam; migration is the soul of their prosperity; change of residence the essential of their existence; whilst a blockade in the interior soon terminates in degeneration and death. I repeat it. The entozoa constitute a specialised fauna. What our native country is to ourselves, the bodies of animals are to them. To attack, to invade, to infest, is their legitimate prerogative. Their organisation, habits, and economy are expressly fashioned to this end. How remarkable and complex is their structure, and how peculiar, diverse, and varied are their ways and wanderings, the contents of this volume will, I trust, sufficiently explain. The puerile horror which even some scientific persons affect to display in regard to the subject is altogether out of place. To the rightly balanced mind the study of these much abused “worms” is just as attractive as any other section of zoology. Helminthology opens up to our view many of the strangest biological phenomena of which the human mind can take cognisance; whilst a profound and extended knowledge of the subject, in all its bearings, is calculated to secure to the community a rich practical reward by enabling us to do effectual battle with not a few of the many ills of life to which our flesh is heir.

Further on the general advantages to be derived from the study of parasites I cannot here dilate, and it becomes the less necessary that I should do so, since I have entered upon the subject very fully elsewhere. The character of the present work, moreover, imposes brevity. If the plan which I now propose to follow should not be deemed altogether satisfactory from the purely zoological standpoint, it will nevertheless have the advantage of simplicity and novelty; and knowing full well the difficulties that must surround any attempt to give a perfect classification of the entozoa, considered as a natural group, I feel sure that my helminthological friends will credit me with exercising a wise discretion in selecting the simplest available method of arrangement. My plan, therefore, is to devote separate sections of this work to the parasites of the different classes of vertebrated animals, including man, treating of the various species in regular succession. This arrangement is merely one of convenience and has no reference whatever to conceptions of zoological equivalency as variously interpreted and maintained by authors and investigators. The parasitic groups will be taken up in the following order, quite irrespective of their relative importance, and also without any attempt to treat each group with equal fulness. In the matter of recent literature only will the present record and summary make any approach toward completeness, my hope being to render this treatise indispensable and trustworthy as a ready means of reference.

I. Flukes. Trematoda.—This group embraces several families of parenchymatous worms. The various species exhibit one or more suckers, which the older naturalists regarded as so many mouths or perforations. Hence the ordinal title. The term fluke is of Saxon origin, meaning anything flat. Thus, it has been applied to sole-fish or flounders, to the flattened halves of the tail of cetaceans, to the blades of anchors, and so forth. Although the common liver fluke is flat, many species of the order are round, biconvex, or even filiform organisms. I recognise six families:—Monostomidæ, Distomidæ, Amphistomidæ, Tristomidæ, Polystomidæ, and Gyrodactylidæ. Most of the species are entozoal; but many adhere to the surface of the body of piscine hosts.

II. Tapeworms. Cestoda.—This comprises not only the tapeworms, but also the measles and other bladder-worms or cystic Entozoa of the old authors (Cystica). The Greek word kestos means a band or girdle; hence the ordinal term above given. The bladder-worms, including Hydatids, Cysticerci, &c., are the larval stages of growth of various tapeworms. The further reduction of this order into sub-orders or families requires careful attention. At present we have Tæniadæ, Acanthotæniadæ, Dibothridæ (= Bothriocephalidæ), Diphyllobothridæ, Tetrarhynchidæ, and Tetraphyllobothridæ. All the genera and species are entozoal. The proposal to separate the snouted or proboscidiform tapeworms (Rhynchotæniadæ) from those in which the rostellum is absent (Arhynchotæniadæ) does not recommend itself to my judgment.

III. Roundworms. Nematoda.—This series comprises not only lumbricoid or roundworms proper, but also threadworms. The term derives its origin from the Greek word nema, signifying a thread. It likewise includes the strongyles, the term strongulos meaning round or cylindrical. This is a very extensive group whose parasitic members are strictly entozoal, whilst the non-parasitic forms are either entirely free or they infest plants. Some of the so-called free nematoids live in the slime of animals. The artificial classification by Schneider, based on the muscular system, places these parasites in three well-marked groups, but I think it a disadvantage to separate widely many really closely allied forms. Thus, in his Polymyarii we have the genus Enstrongylus, and in his Meromyarii the Strongyli proper. Most of the genera may be fairly included in the following families:—Ascaridæ, Cheiracanthidæ, Cucullanidæ, Strongylidæ, Trichinidæ, Oxyuridæ, Trichocephalidæ, Filaridæ, Gordiidæ, Anguillulidæ.

IV. Thornheaded-worms. Acanthocephala.—This group embraces a small series of parasites, which, in general appearance, resemble the nematode worms. They differ, however, essentially, being, as the term indicates, furnished with spine-covered heads. They are, moreover, destitute of digestive organs. The species are entozoal in habit, abounding particularly in fishes and reptiles. At present, all the known forms are included in one family (Echinorhynchidæ), which also comprises only a single genus.

V. Annelid Parasites. Suctoria.—In this category one must place all such suctorial annelids as affix themselves to hosts for a longer or shorter period. Many of the leech-like parasites (Clepsinidæ, and especially Malacobdellidæ) remind one of certain flukes (Tristoma, &c.) possessing ectozoal habits; whilst the leeches, properly so called, afford instances of the passage from a semi-parasitic to what has been called the free parasitic mode of existence. In tropical countries these creatures very readily attach themselves to man and animals, often creating severe distress. The genera Clepsine and Hæmocharis attack mollusks and fishes respectively. The species are all ectoparasitic and exceedingly numerous. They cannot be described in this work.

VI. Arachnid parasites, Arachnida (part of).—The great class of articulated, limb-jointed, or, more strictly, arthropodous animals, includes a variety of parasites. The mites, true ticks, and such like creatures, belong to this group. Some few of them are entozoal in habit, others are only partially so, whilst the majority are entirely ectozoal. Of the two great sections of Arachnida, namely, Pulmonaria and Trachearia, the latter alone contains strictly parasitic forms. The parasitic species belong to the following families:—Pentastomidæ, Pycnogonidæ, Ixodidæ, Acaridæ, Gamasidæ, Hydrachnidæ, Solpugidæ. The parasitism of some of the species is very partial or slight. Thus, certain of the water mites, in their juvenile state, dwell on aquatic insects only; and the tick-like Gamasidæ occur upon dung-beetles. The other ectozoal species attack vertebrated animals, and several attach themselves to man himself. The whale lice (Cyamidæ) are here included in the Pycnogonidæ, though often placed by zoologists with the Crustaceans.

VII. Crustacean Parasites. Crustacea (part of).—A large number of species belonging to various well-marked sections of this great class of Invertebrates are parasitic in their habits, most of them being comprised in the so-called haustellated group. They are familiarly known to zoologists as Epizoa. As this latter term implies, they are strictly ectozoal in character, most of the species victimising fishes by attaching themselves, not only to the general surface of the body, but also to the eyes, and especially to the gills or branchiæ. The species for the most part belong to the families Lernæidæ, Caligidæ, Dichelestidæ, and Argulidæ. In this category must likewise be placed two other families belonging to the so-called isopodous section of edriophthalmatous crustaceans. These are the Cymothoidæ, which attach themselves to the tails of fishes, and the Bopyridæ, which occupy the branchial cavity of shrimps. The nature of this work precludes any detailed notice of the numerous members of this section.

VIII. Insect Parasites. Insecta (part of).—The insects, properly so called (that is to say, arthropodous, evertebrated creatures, with six legs), are many of them essentially parasitic in their habits. The most important of these are “bots” and other larvæ or maggots of various flies (Diptera). The varieties of lice are also included in this group. Some few of the insect parasites are strictly entozoal in habit, at least for a part of their lifetime, being previously attached externally for a short period only. Most of the forms are essentially ectozoal. A very large number of insect tormentors, although deriving nourishment from their victims, attach themselves to the animals for so short a time that they cannot be classed as parasites under the ordinary acceptation of the term. As examples of the so-called free parasitism, the autumnal flies (Tabanidæ) and Stomoxys may be cited. Although embracing but few strictly parasitic forms we have the following:—Œstridæ, Hippoboscidæ (with Melophagus), and Nycteribiidæ. In regard to the maggots of Muscidæ and Sarcophagæ, some of them are parasitic on animals and man, whilst others are parasitic upon insects themselves. The larvæ of Conopidæ attack humble-bees internally. Those parasitic insects, properly so called, which, like certain of the crustaceans, are sometimes spoken of as epizoa, comprise three well-marked families. Thus, we have Pediculidæ (the source of lousiness), Philopteridæ, and Liotheidæ. Both of the latter embrace numerous species which for the most part content themselves with devouring the feathers of birds and the hairs of quadrupeds. In addition to these it may be added that some of the rat-tailed larvæ or Helophilus maggots (Syrphidæ) are parasitic in man and quadrupeds, as are also the larvæ of the churchyard beetle (Blaptidæ). The closely allied Tenebrionidæ and other coleopterous families also supply various maggots possessed of parasitic habits. Fleas and bugs come under Van Beneden’s category of free parasites. This is equivalent to calling them non-parasitic parasites, an expression which looks very like a contradiction of terms.

IX. Protozoal Parasites. Protozoa (part of.)—This miscellaneous assemblage of minute creatures embraces a number of parasites of very low organisation. In the present work it is neither desirable nor necessary to hazard any statements respecting their precise zoological position. It is sufficient to say that the parasitic protozoa are for the most part entozoal in habit, not a few of them possessing vegetable affinities. The microscopic Bacteridæ, Gregarinidæ, and Psorospermiæ, comprise a multitude of organisms which are strictly parasitic in their habits, whilst amongst the Infusoria we find numerous forms which, though dwelling in the intestinal canal of their hosts, do not derive nourishment in a direct manner from their bearers. Of this kind are Paramecium and Balantidium. The separation of the psorospermiæ and gregarinæ into genera is attended with difficulty; nevertheless, I have for convenience long recognised various types under titles corresponding with the names of the observers who first discovered them (Hesslingia, Gubleria, Lindermannia, and so forth). Of necessity, the protozoal parasites will only be incidentally noticed in this work. In this category I place the falsely so called “cattle-plague bodies.” The micrococci and bacteria hardly come within the province of the helminthologist.

Without prejudice to the foregoing restrictions I must at the same time observe that the varied characters presented by the above-mentioned groups show how impossible it is to treat the subject of parasitism adequately, if one is obliged to confine his remarks to the internal parasites or helminths proper. Many creatures possessed of entozoal and ectozoal habits are parasites in every legitimate sense of the term, and yet they do not belong to the class Helmintha in its common zoological acceptation. That class taken by itself may still be allowed to stand pretty much as I represented it in 1864; but in the present work I cease to speak of the Entozoa as in any sense the zoological equivalent of the Helmintha. I prefer to employ the term Entozoa in its popular and wider acceptation. It conveniently stands thus, moreover, in direct contradiction to the term Ectozoa.

As this work treats of parasites only, I purposely refrain from dealing with the Turbellarians, and certain other creatures usually classed with Vermes. The vague term “worms,” so often employed as the equivalent of Helmintha, is misleading in many ways. I should like to see it adopted only when speaking of the Annelids proper. It would still have a sufficiently wide application, seeing that it would include Leeches, Earth-worms, Naids, Tubed-worms, Sea-lobworms, Sea-mice, Nereids, and a host of other setigerous species. Notwithstanding the remote connection subsisting between “intestinal worms” and worms properly so called, the notion that an intimate relation subsists between the lumbricoid helminths and earth-worms will probably never entirely disappear from the popular or even from the professional mind.

Since one of the principal features of this treatise is to afford a handy means of reference to the rich and extended literature of parasitism, I here subjoin a list of general and systematic treatises. To most of these I shall constantly refer. Full special references to detached memoirs will appear in the bibliographies scattered throughout the body of the work.

Bibliography (No. 1).—Bremser, ‘Ueber lebende Würmer im lebenden Menschen,’ Vienna, 1819; French edit., by Grundler, 1824.—Idem, ‘Icones helminthium,’ Vienna, 1824.—Cobbold, T. S., ‘Entozoa, an Introduction to the Study of Helminthology, with reference more particularly to the Parasites of Man,’ London, 1864; Supp., 1869.—Reviews in the ‘Lancet,’ Sept. 24th, 1864, p. 353; in the ‘Med. Times and Gaz.,’ Oct. 29th, 1864, p. 474; in the ‘Athenæum,’ Oct. 15th, 1864, p. 493; in ‘Cosmos,’ Oct. 27th, 1864, p. 463; in the ‘Reader,’ Nov. 26th, 1864, p. 668; in the ‘Edinburgh Vet. Review,’ Nov., 1864, p. 662; in ‘Intellectual Observer,’ vol. vi, 1864, p. 190; in the ‘Quarterly Journal of Science,’ No. v, January, 1865, p. 145; in the ‘Quart. Journ. of Micr. Science,’ New Series, No. 17, Jan., 1865, p. 43; in ‘Popular Science Review,’ Jan., 1865, p. 214; in the ‘Veterinarian,’ Feb., 1865, p. 97; in the ‘Medical Mirror,’ Jan., 1865, p. 23; in the ‘Natural History Review’ for July, 1865; in the ‘British and Foreign Medico-Chirurgical Review,’ April, 1865, in the ‘Edinburgh Medical Journal’ for April, p. 929; in the ‘Social Science Review’ for Feb. 1, 1866, p. 169; in ‘Dublin Quart. Journ. of Medical Science’ for Aug., 1867.—Davaine, C., ‘Traité des Entozoaires et des maladies vermineuses de l’homme et des animaux domestiques,’ Paris, 1860, 2nd edit., 1877–79.—Diesing, C. M., ‘Systema helminthum,’ Vienna, 1850.—Dujardin, F., ‘Histoire naturelle des helminthes ou vers intestineaux,’ Paris, 1845.—Goeze, T. A. S., ‘Versuch einer Naturgeschichte der Eingeweidewürmer thierischer Körper,’ Blankenburgh, 1782.—Küchenmeister, F., ‘Die in und an dem Körper des lebenden Menschen vorkommenden Parasiten,’ Leipsic, 1855, 2nd. edit., 1878–79; Eng. edit., by Lankester, 1857.—Le Clerc, D., ‘A Natural and medicinal History of Worms bred in the bodies of men and other animals’ (sic), Browne’s edit., London, 1721.—Leuckart, R., ‘Die menschlichen Parasiten, und die von ihren herruhrenden Krankheiten,’ Leipsic und Heidelberg, 1863–1876.—Redi, F., ‘De animalculis vivis quæ in corporibus animalium vivorum reperiuntur, observationes;’ Coste’s edition, Amstelædami, 1688.—Rudolphi, C. A., ‘Entozoorum sive vermium intestinalium historia naturalis,’ Amsterdam, 1808.—Idem, ‘Entozoorum Synopsis,’ Berlin, 1819.—Van Beneden, P. J., ‘Animal Parasites and Messmates,’ London, 1876.

Several of the above works, while professing to deal with human parasites only, cover more or less of the whole ground of helminthology. Leuckart’s work is invaluable in this respect; and in the matter of literary references of a professional kind Davaine’s treatise is itself well nigh exhaustive. In any ordinary volume it is not possible to give a complete bibliography of parasitism. I make no pretension to do so here; nevertheless, the large number of modern memoirs that I have received from the distinguished writers themselves, enables me to render this part of my book very useful. As second only in importance to the above-mentioned works may be added the following—whether minor treatises, memoirs, monographs, comprehensive articles, or reports of a general or special character, respectively. As such it will be seen that some of them are sufficiently comprehensive, and their mere enumeration will enable the beginner to realise something like a fair estimate of the scope of helminthology. In the case of my own works I have ventured to add references to reviews and notices, because many of the latter contain valuable original suggestions made by the various anonymous writers.

Bibliography (No. 2).—Bastian, H. C., “On the Anatomy and Physiology of the Nematoids, parasitic and free,” ‘Philosophical Transactions,’ 1865 (see also Bibliog., No. 60).—Cobbold, T. S., ‘Worms; a series of lectures on Practical Helminthology,’ London, 1872; Italian edition by Tommasi. Milan, Florence, &c., 1873.—Idem, ‘The Internal Parasites of our Domesticated Animals,’ London, 1873; Italian edit. by Tommasi, Florence, 1874.—Idem, ‘Tapeworms (Human), their Sources, Varieties, and Treatment,’ London, 3rd edit., 1875. Reviews (1st and 2nd edit., with ‘Threadworms’), in ‘Brit. and For. Med.-Chir. Review’ for 1867, p. 433; in ‘Edin. Med. Journ.’ for 1866–67, p. 107; in ‘Lancet,’ Nov. 10th, 1866; in ‘Popular Science Review,’ Oct. 1st, 1866; in ‘Intellectual Observer,’ Oct. 1866; in ‘Med. Press and Circular,’ Jan. 16th, 1867; again in the ‘Lancet,’ for March 13th, 1867; and in ‘Dublin Quart. Journ. of Medical Science’ for 1867, 3rd edit.; in the ‘Field,’ Sept. 25th, 1875; and in ‘Popular Science Review’ for Jan., 1876.—Idem, ‘Catalogue of the Specimens of Entozoa in the Museum of the Royal College of Surgeons of England,’ London, 1866; noticed in the ‘Lancet’ for March 24th, 1866, p. 321.—Idem, “On the best Methods of displaying Entozoa in Museums,” ‘Journ. Linn. Soc.,’ vol. viii, p. 170.—Idem, ‘New Entozootic Malady,’ &c., 1864; popular brochure, reviewed in the ‘Lancet,’ Feb. 4th, 1865, p. 128; in the ‘Athenæum,’ Jan. 21st, 1865, p. 87; in the ‘British Med. Journal,’ Jan., 1865; in the ‘Veterinary Review and Stockowners’ Journal,’ No. 2, New Series, Feb., 1865, p. 76; in the ‘Reader,’ Feb. 4th, 1865, p. 142; in ‘Med. Times and Gaz.’ for June 2nd, 1865; in the ‘Field’ for March 18th, 1865.—Idem, “Parasites of Man,” forming a series of articles contributed to the ‘Midland Naturalist,’ 1878–79.—Idem, “Notes on Entozoa contained in the various Metropolitan Museums,” in ‘Lancet,’ May 13th, 1865, p. 503.—Idem, “Report on Plica polonica, in reference to Parasites,” in ‘Pathological Soc. Trans.,’ 1866, p. 419.—Idem, “Report on Experiments respecting the Development and Migrations of the Entozoa,” ‘British Assoc. Reports’ (Bath Meeting) for 1864, p. 111; and briefly noticed in ‘Lancet’ for Sept. 24th, 1864.—Idem, Miscellaneous observations, including “Note on Parasites in the Lower Animals,” in ‘Dub. Med. Press’ for Feb. 11th, 1863, p. 154.—Idem, “Vegetables, Fruits, and Water considered as sources of Intestinal Worms;” in the ‘Popular Science Review’ for Jan., 1865, p. 163.—Idem (anonymously), “On Comparative Pathology and Therapeutics” (in relation to Entozoötics); leading art. in ‘Lancet’ for Dec. 9th, 1865, p. 652.—Idem, “List of Entozoa, including Pentastomes, from animals dying at the Zoological Society’s Menagerie, between 1857–60 inclusive, with descriptions of several new species,” ‘Proc. Zool. Soc.,’ 1861.—Idem, “Remarks on all the Human Entozoa,” ‘Proc. Zool. Soc.,’ 1862; abstracts in ‘Brit. Med. Journ.’ for 1862, and in ‘Edinb. New Phil. Journ.,’ vol. xvii, new series, 1863, p. 145; in Report of the ‘Proceed. of the Brit. Assoc. at Cambridge,’ 1862.—Idem, “Our Food-producing Ruminants, and the Parasites which reside in them; being the Cantor Lectures of the Society for the Encouragement of Arts, Manufactures, and Commerce,” delivered in 1871, and pub. in the ‘Journal of the Soc. of Arts’ for that year.—Davaine, C., “Les Cestoïdes,” in ‘Dict. Encycl. des Sci. Med.,’ Paris, 1876.—Eberth, C. J., ‘Untersuchungen ueber Nematoden,’ Leipsic, 1863.—Heller, A., “Darmschmarotzer,” in Von Ziemssen’s ‘Handbuch,’ Bd. vii, 1876; and in the American edition of the same, 1877.—Jones, T. R., “List of Entozoa of Greenland,” taken from Krabbe; ‘Arctic Manual,’ 1875, p. 179.—Krabbe, H., ‘Helminthologiske Undersogelser,’ Copenhagen, 1865.—Leuckart, R., ‘Die Blasenbandwürmer und ihre Entwicklung,’ Giessen, 1856.—Moquin-Tandon, A., “Epizoa and Entozoa,” in Hulme’s edit. of his ‘Elements of Medical Zoology,’ London, 1871.—Nordmann, A. von, ‘Mikrographische Beiträge zur Naturgeschichte der wirbellosen Thiere,’ Berlin, 1832.—Olsson, P., “Entozoa, iakttagna hos Skandanaviska hafsfiskar.,” Lund, ‘Univ. Årsskrift,’ 1867.—Owen, R., “Entozoa,” art. in Todd’s ‘Cyclopædia of Anat. and Physiol.,’ London, 1839.—Idem, “Entozoa,” ‘Lectures (iv and v) on the Comp. Anat. and Physiol. of the Invertebrate Animals,’ London, 1855.—Pagenstecher, H. A., ‘Trematodenlarven und Trematoden,’ Heidelberg, 1857.—Rhind, W., ‘A Treatise on the Nature and Cure of Intestinal Worms, &c.,’ London, 1829.—Rolleston, G., “Characteristics of Nematelminthes and Platyelminthes,” in his ‘Forms of Animal Life,’ Oxford, 1870.—Schneider, A., ‘Monographie der Nematoden,’ Berlin, 1866.—Siebold, C. von., “Parasiten,” art. in Wagener’s ‘Handwörterbuch der Physiol., &c.,’ 1845.—Idem, “Helminthes,” Book v, in Burnett’s edit. of Siebold and Stannius’ ‘Comparative Anatomy,’ London and Boston, 1854.—Thomson, A., “Entozoa,” in the art. “Ovum,” in Todd’s ‘Cyclop. of Anat. and Physiol.,’ London, 1859.—Van Beneden, P. J., ‘Mémoire sur les Vers Intestineaux,’ Paris, 1858.—Idem, “Les Vers Cestoïdes,” ‘Mém. de l’Acad. Roy.,’ Brussels, 1850.—Verrill, A. E., “The External and Internal Parasites of Man and the Domestic Animals,” ‘Rep. of Board of Agriculture,’ Connecticut, U.S., 1870.—Von Baer, K. E., ‘Observations on Entozoa;’ in an analytical notice of his article “Beiträge zur Kentniss der niedern Thiere,” from ‘Nova Acta Nat. Cur.,’ tom. xiii, in the ‘Zool. Journ.,’ vol. iv, p. 250, 1828–29.—Wagener, G. R., ‘Beiträge zur Entwicklungsgeschichte der Eingeweidewürmer,’ Haarlem, 1857.—Weinland, D. F., ‘An Essay on the Tapeworms of Man,’ Cambridge, U.S., 1858.

BOOK I.

PARASITES OF MAN.

Whatever notions people may entertain respecting the dignity of the human race, there is no gainsaying the fact that we share with the lower animals the rather humiliating privilege and prerogative of entertaining a great variety of parasites. These are for the most part entozoal in habit. As the parasites are apt to cause suffering to the bearer, a superstitious age sought to interpret their presence as having some connection with human wrong-doing. We can now afford to smile at such erroneous ideas. The intimate relation subsisting between parasitic forms dwelling in man and animals, and their interdependence upon one another, alone suffices to preclude the idea that parasites have been arbitrarily placed within the human bearer. It would seem, indeed, that our existence is essential to the welfare and propagation of certain species of parasites. Possibly it is only by accepting the hypothesis of “Natural Selection” that we can escape the somewhat undignified conclusion that the entozoa were expressly created to dwell in us, and also that we were in part designed and destined to entertain them. View the matter as we may, the internal parasites of man and animals strictly conform to a few well-known types of structure, but these types branch out into infinitely varied specific forms. The vulgar mind sees nothing attractive in the morphology and organisation of a parasitic worm, and common-place conceptions of the beautiful cannot be expected to embrace within their narrow grasp the marvelous harmony and order that pervade the structure and economy of the individual members of this remarkable class of beings.

SECTION I.—Trematoda (Flukes).

Fasciola hepatica, Linneus.—The first form I have to consider is the common liver fluke. The part this entozoon plays in the production of disease will be fully stated when treating of the parasites of the sheep and other ruminants. About twenty instances of its occurrence in the human body have been recorded. It has been found beneath the skin in the sole of the foot (Giesker), and also under the scalp (Harris), and behind the ear (Fox). Its more frequent seat is in the liver and gall-ducts (Pallas, Brera, Bidloo, Malpighi) and gall-bladder (Partridge). The alleged cases by Bauhin, Wepfer, and Chabert are spurious, as is probably also that given by Mehlis. Duval’s case appears to be genuine, but the occurrence of the worm in the portal vein was accidental. Dr Murchison has recorded a case, occurring at St Thomas’s Hospital, where a solitary specimen was found in the liver. Dr H. V. Carter also met with the worm in a young Hindoo.

In the second half of the present work I shall reproduce Blanchard’s admirable figure of the sexually mature worm (Fig. [61]), accompanied by a categorical statement respecting the known facts of development. In this place, however, I may observe that the cases recorded by Giesker, Harris, and Fox had clearly pointed to the circumstance that the higher larvæ of this fluke must be armed cercariæ, otherwise they could not have bored their way through the human skin. As we shall see, Dr Willemoes-Suhm’s investigations have furnished evidence as to the truth of this supposition. For anatomical details I refer to my introductory treatise. In the adult state the liver fluke has been known from the earliest times. We have clear evidences that it was described by Gabucinus in the year 1547, and also subsequently by Cornelius Gemma, who, in a work published some thirty years later, refers to an epizootic disease prevalent in Holland during the year 1552, and which was very justly attributed to the parasite in question. After this date many writers described the liver fluke more or less accurately, and entire volumes were devoted to the consideration of the formidable disease which it occasions. The nomenclature of the parasite has been a subject of controversy. Amongst naturalists in general the common liver fluke is often described under the combined generic and specific name of Distoma hepaticum; but the title is both incorrect and inappropriate. The proper generic appellation of this parasite is Fasciola, as first proposed by the illustrious Linneus (1767) and subsequently adopted by F. Müller (1787), Brera (1811), Ramdohr (1814), and others. Unfortunately Retzius (1786) and Zeder (1800) changed the generic title without good cause, and the majority of writers, following their authority, refused to employ the original name, although a consideration of the distinctive types of structure severally displayed by the genera Distoma and Fasciola fairly demanded the retention of the Linnean title. In later times M. Blanchard (1847) strongly advocated the original nomenclature, and I have myself continually urged its adoption. On somewhat different grounds Professor Moquin-Tandon followed the same course.

In the sexually mature state the liver fluke commonly measures three fourths of an inch in length, occasionally reaching an entire inch or even sixteen [lines]; its greatest breadth also varying from half an inch to seven or eight lines transversely; body very flat, presenting distinct dorsal and ventral surfaces, frequently curled toward the latter during life; upper or anterior end suddenly constricted, produced and pointed in the centre, forming the so-called head and neck; posterior extremity less acuminated, sometimes rounded, or even slightly truncated; margins smooth, occasionally a little undulated, especially towards the upper part; oral sucker terminal, oval, rather smaller than the ventral acetabulum, which is placed immediately below the root of the neck; reproductive orifices in the middle line, a little below the oral sucker; intromittent organ usually protruded and spirally curved; a central, light-coloured space, covering two thirds of the body from above downwards, marks the region of the internal male reproductive organs, being bordered on either side and below by a continuous dark band, indicating the position of the so-called yolk-forming organs; a small, brown-coloured, rosette-like body situated directly below the ventral acetabulum, marks the limits of the uterine duct; a series of dark lines, branching downwards and outwards on either side, indicate the position of the digestive organs; general color of the body pale brownish yellow, with a slight rose tint. The surface of the body, though smooth to the naked eye, is clothed throughout with small epidermal spines which diminish in size towards the tail.

If any argument were necessary to show how desirable it is to furnish full descriptions of the commoner kinds of parasite, I could adduce numerous instances that have been brought under my notice where professional men and others have been entirely mistaken as to the essential nature of their parasitic finds. Thus, I have known an instance where a great authority on the diseases of dogs has persisted in asserting for the free proglottides of a tapeworm a nematode origin; and, in like manner, human tapeworm-segments have frequently been mistaken for independent fluke parasites. One of the most remarkable instances of this kind is that which I have elsewhere described as an error on the part of Dr Chabert. My reasons for so regarding his interpretation of the facts observed by him stand as follows:

In the ‘Boston Medical and Surgical Journal’ for the years 1852–53–54, Dr J. X. Chabert described several cases of Tænia, and he averred that the tapeworms were associated with numerous specimens of Distoma hepaticum. The passage of distomes by patients during life was even regarded by Dr Chabert as indicative of the presence of Tænia within the intestines. Surely, I remarked, Dr Chabert was mistaken. Are not these so-called distomes the well-known proglottides? Not willingly doubting Dr Chabert’s statements, but desirous, if possible, of verifying the accuracy of his conclusions, I wrote to him (March 22nd, 1864) requesting the loan of a specimen, but I was not fortunate enough to receive a reply. In the “Case of Tænia” in a boy four and a half years old, given in the 49th vol. of the journal, Dr Chabert writes as follows:—“In consequence of his passing the Distoma hepaticum, I concluded he must be afflicted with Tænia.” Further on it is added, that the administration of an astringent injection “caused the discharge of innumerable small worms (Distoma hepaticum).” I think this is quite decisive. The idea of “innumerable” flukes being expelled in this way is altogether out of the question.

The only genuine case in which any considerable number of Distomata, of this species, have been observed in the human subject is the one recently recorded by Dr Prunac. In this instance two flukes were vomited along with blood immediately after the administration of salines (sel de Seignette), and about thirty were passed per anum. On the following day, some tapeworm proglottides having been evacuated, both salts and male-fern extract were administered. This caused the expulsion of an entire tapeworm, and also about twenty more flukes. Notwithstanding this successful treatment the hæmatemesis returned in about a month, when, finally, three more flukes were vomited and the bleeding ceased. Had not the parasites been submitted for identification to a competent observer (Prof. Martins, of Montpellier), some doubt might have been entertained as to the genuineness of this remarkable case. In reference to Dr Prunac’s comments on the facts of fluke-parasitism in man, I will only remark that Dr Kerr’s Chinese cases, to which he refers, were probably due to Distoma crassum and not to D. hepaticum. The Chinese flukes will be noticed below.

Bibliography (No. 3).—Full references to details of the cases by Partridge, Fox, and Harris are given in Appendix B. to Lankester’s Edit. of Küchenmeister’s Manual. See also the works of Davaine and Leuckart (l. c. Bibl. No. 1).—Carter, H. V., “Note on Distoma hepaticum” (from a patient under the care of Mr Pandoorung), ‘Bombay Med. and Physical Soc. Trans.’ (Appendix), 1862.—Chabert, J. X. (quoted above). Murchison, C., ‘Clinical Lectures on Diseases of the Liver,’ (2nd Edit., Appendix), London, 1877.—Prunac, De la Douve ou Distome hépatique chez l’homme; in ‘Gazette des Hôpitaux’ for December, 1878 (p. 1147). For further references in this work, see Bibliog. No. [49].

Fig. 1.—The lancet-shaped fluke (Dis­to­ma lan­ce­o­la­tum), show­ing the dis­po­si­tion of the di­ges­tive and re­pro­duc­tive or­gans in­tern­ally. Viewed from behind; mag. about 12 diameters. After Blanchard.

Distoma lanceolatum, Mehlis.—At least three instances of the occurrence of this small fluke in the human body have been observed. The authority for these cases rests, severally, with Bucholz, who found them in the gall bladder in considerable numbers at Weimar; with Chabert, who expelled a large number from the intestines of a girl in France; and with Küchner, who obtained forty-seven specimens from a girl in Bohemia. Probably many similar instances have been overlooked, and Küchenmeister hints that Duval’s parasites (above mentioned) may have been this species. Although this worm will again be incidentally noticed in connection with bovine parasites (and its ciliated larvæ will also be referred to when discussing the characters of the embryo of Bilharzia), I here subjoin a diagnosis of the characters of the adult parasite. The lancet-shaped liver fluke is a small flat helminth, measuring rather more than the third of an inch in length, and about one line and a half in breadth, being also especially characterised by its lanceolate form; the widest part of the body corresponds with a transverse line drawn across the spot where the vitellaria terminate below, and from this point, on either side, the width of the animal becomes gradually narrowed towards the extremities; both ends are pointed, but the inferior or caudal one more obtusely than the anterior or oral end; the general surface is smooth throughout, and unarmed; the reproductive orifices are placed in the central line immediately in front of the ventral sucker, and below the point at which the intestine bifurcates; the oral sucker is nearly terminal, and 1/50″ in breadth, the ventral acetabulum being about the same diameter; the testes form two lobed organs placed one in front of the other in the middle line of the body and directly below the ventral sucker; the uterine canal is remarkably long, forming a series of tolerably regular folds, which occupy the central and hinder parts of the body, reaching almost to the caudal extremity. The vitelligene glands cover a limited space, on either side of the centre of the body near the margin. The foramen caudale communicates with a contractile vesicle, which passes upwards in the form of a central trunk-vessel, early dividing into two main branches; these latter reach as far forwards as the œsophageal bulb, opposite which organ they suddenly curve upon themselves, retracing their course for a considerable distance backwards; the digestive canals are slightly widened towards their lower ends, which occupy a line nearly corresponding with the commencement of the lower fifth of the body; the ova are conspicuous within the uterine folds, which present a dark brownish color in front, passing to a pale yellow color below.

In reference to Kichner’s remarkable case I reproduce an abstract of it from Leuckart’s account (‘Die menschlichen Parasiten,’ Bd. i, s. 608), the original particulars of which were communicated to Leuckart by Dr Kichner himself:—

“Dr Kichner’s patient was a young girl, the daughter of the parish shepherd at Kaplitz, having been accustomed to look after the sheep ever since she was nine years old. The pasture where the animals fed was enclosed by woods, being traversed by two water dykes, and being, moreover, also supplied by ten little stagnant pools. These reservoirs harboured numerous amphibia and mollusks (such as Lymnæus and Paludina), and the child often quenched her thirst from the half putrid water. Probably she also partook of the watercresses growing in the ditches. At length her abdomen became much distended, the limbs much emaciated, and her strength declined. Half a year before death she was confined to her bed, being all the while shamefully maltreated by her step-mother. Dr Kichner only saw her three days before her death, and ascertained that she had complained of pain (for several years) over the region of the liver. A sectio cadaveris was ordered by the Government, when (in addition to the external evidences of the cruel violence to which the poor creature had been subjected) it was found that she had an enormously enlarged liver, weighing eleven pounds. The gall-bladder which was very much contracted and nearly empty, contained eight calculi and forty-seven specimens of the Distoma lanceolatum, all of which were sexually mature.”

As I have remarked in a former comment on this singular case, one can have no difficulty in arriving at the conclusion that these parasites were obtained from the girl’s swallowing trematode larvæ, either in their free or in their encysted condition. Leuckart says it was not possible to ascertain whether the parasites had any connection with the gall-stones, or whether the two maladies, so to speak, were independent of each other; yet this question might possibly have been solved if the calculi had been broken up in order to ascertain their structure. It is just possible that dead distomes may have formed their nuclei, and if so, the circumstance would, of course, point to the worms as the original source of the malady.

So far as I am aware, the actual transformations undergone by the larvæ of Distoma lanceolatum have not been observed. The Planorbis marginatus has been confidently referred to as the intermediate bearer of the cercariæ of the common fluke, and Leuckart supposes that the same mollusk harbours the larvæ of this species. The ciliated embryos carry a boring spine or tooth, and it is most probable that the higher larvæ are similarly armed.

Bibliography (No. 4).—Kichner (see Leuckart), quoted above.—Cobbold, ‘Entozoa’ (p. 187).—The case by Bucholz (reported as one of Fasciola hepatica) is given by Jördens in his work (quoted by Diesing and Leuckart) ‘Entomologie und Helminthologie des menschlichen Körpers,’ (s. 64, tab. vii, fig. 14), 1802.—Chabert’s French case is quoted by Rudolphi in his ‘Entozoorum sive vermium,’ &c. (loc. cit., Bibl. No. 1), p. 326, 1808.

Distoma crassum, Busk.—This large species was originally discovered by Prof. Busk in the duodenum of a Lascar who died at the Seamen’s Hospital, 1843. It, however, remained undescribed until 1859, when, with the discoverer’s approval, I gave some account of it to the Linnean Society.

Of the fourteen original specimens found by Mr Busk, several have been lost. The one that he himself gave me I handed over to Prof. Leuckart, and it is figured in his work (‘Die mensch. Par.,’ s. 586). A second is preserved in the museum attached to the Middlesex Hospital, and a third is contained in the Museum of the Royal College of Surgeons. This last-named specimen is the best of the original set. It supplied me with the few details of structure figured in outline in my ‘Introductory Treatise’ (fig. 42, p. 123), published in 1864; and it also in part formed the basis of the description of the species communicated to the Linnean Society in June, 1859 (“Synopsis of the Distomidæ,” p. 5, ‘Proceedings,’ vol. v). The late Dr Lankester, it is true, was the first to give a distinctive title to this entozoon (Distoma Buskii); but as the discoverer objected to this nomenclature, and as Dr Lankester’s proposed terms were unaccompanied by any original description, I requested Mr Busk to suggest a new name for the worm, which he accordingly did. As I subsequently pointed out, Von Siebold had already employed the compound title Distoma crassum to designate a small fluke infesting the house-martin (Hirundo urbica); but for reasons similar to those which contributed to set aside Dr Lankester’s nomenclature, the title adopted in my synopsis at length came to be recognised by Leuckart and by other well-known helminthologists. Before this recognition took place, Dr Weinland, of Frankfort, had so far accepted Lankester’s nomenclature as to call the species Dicrocœlium Buskii. In my judgment there are no sufficient grounds for retaining Dujardin’s genus. Further, I may observe that, in addition to the above-mentioned specimens, two others are preserved in the Museum at King’s College. Thus, only five out of the fourteen specimens are still in existence.

No well-authenticated second instance of the occurrence of this worm took place until the year 1873, when a missionary and his wife from China consulted Dr George Johnson respecting parasites from which they were suffering. After a brief interval, both of Dr Johnson’s patients were by an act of courtesy on the part of this eminent physician placed under my professional care. I need hardly add that Dr Johnson had from the very first recognised the trematode character of the parasites. From the patients themselves I ascertained that they had been resident in China for about four years. During that period they had together freely partaken of fresh vegetables in the form of salad, and also occasionally of oysters, but more particularly of fish, which, in common with the oysters, abound in the neighbourhood of Ningpo. From their statements it appeared to me that to one or other of these sources we must look for an explanation of the fact of their concurrent infection. Fluke larvæ, as we know, abound in mollusks and fish; but whether any of the forms hitherto found in oysters or in fish have any genetic relation to the flukes of man, is a question that cannot very well be settled in the absence of direct experimental proof. I should add that it was not until after their visit to the interior of the country, some 130 miles distant from Ningpo, that the symptoms (which Dr Johnson in the first instance, and myself subsequently, considered to have been due to the presence of the parasites) made their appearance. Whilst in the country the missionary and his wife freely partook of freshwater fish, and on one occasion they received a quantity of oysters that had been sent up from Ningpo. The husband assured me that the fish were always thoroughly well cooked.

If it be asked what were the symptoms produced, I can only furnish such few and hitherto unpublished particulars as the missionary himself supplied. I need hardly say that he was a highly cultured and intelligent gentleman, since only such persons are chosen for missionary work in China.

From inquiries made by me on the 29th of January, 1875, I learnt that they left Ningpo in November, 1872, and travelled thence 130 miles into the interior of the country. In the following September, or about ten months subsequently, the missionary was attacked with diarrhœa, which persisted until expulsion of some of the parasites had occurred. According to the patient’s statements this result, so far, was entirely due to his having been placed on a milk diet; this course of treatment having been recommended by Dr Henderson, of Shanghae. The patient himself always suspected the presence of intestinal worms of some sort or other, although a Japanese doctor laughed at the idea of such a thing. Some other doctor treated this missionary for parasites, administering both male-fern and santonine without effect.

It was not until several months had elapsed that his wife was attacked with diarrhœa. In both cases there was more or less flatus. The motions were white, and there were other indications implying that the liver was affected. Later on, symptoms of indigestion, with heartburn, set in and became very severe. Streaks of blood appeared in the fæces, but there was no dysentery. For the most part these symptoms were attributed to the effects of climate.

When, in the month of February, 1875, I saw the missionary a second time, professionally, I found that all the old symptoms had returned. He had a foul tongue, the surface of the body was cold, he felt chills, and the pulse, though regular, registered ninety-six to the minute. Indigestion, nausea, headache, and diarrhœa had reappeared. Notwithstanding these febrile symptoms, so satisfied was the patient himself that all his ailments were entirely due to the presence of parasites, that I felt inclined to take the same view of his case. Accordingly my attention was principally directed to an effort for their expulsion; and in this view I ordered an aloetic pill followed by a castor-oil emulsion. This having no effect, I subsequently prescribed aloes and assafœtida pills, followed by scammony mixture. The action of the latter drug did not occasion griping, but, although efficient, led only to negative results. I should mention that in the patient’s judgment none of the vermifuges administered to him at any time had exerted any influence in the expulsion of the flukes. He was still thoroughly impressed with the notion that the milk diet, ordered by Dr Henderson, was the sole cause of their expulsion.

As even a missionary could not live by milk alone I insisted upon a more substantial diet. The milk, indeed, had occasionally been supplemented by Liebig’s extract of meat and by light farinaceous food. When I last saw him neither he nor his wife had passed any more flukes, but they did not feel satisfied that no more guests remained. Somewhat improved in general health, the missionary resolved to go back to his duties in China. I expressed my fears, however, that his strength would prove unequal to the work.

From the size and almost leathery texture of the two flukes which were in the first instance submitted to my notice, I at once recognised the species; but as they were spirit-specimens, I requested that if any more examples were obtained they should be sent to me in the fresh state. Fortunately others were brought in a few days, when, from an examination conducted whilst they were still fresh, I was able to make out several details of structure which had hitherto escaped notice. Altogether I secured seven specimens, three of them being in a mutilated condition. In what way these mutilations (as shown by my dried specimens) occurred I have not been able to make out, either by personal observation or by questioning the bearers. Two of the parasites look as though portions had been carefully excised near the centre. The new facts I have gleaned were derived from the examination of two comparatively small specimens, one of which, dried, has, by Prof. Rolleston’s desire, been deposited in the anatomical department of the University Museum at Oxford. When I took occasion to bring some of the new specimens under Mr Busk’s attention, he at once recognised them as referable to the species he had long ago discovered.

The earliest literary notice of Distoma crassum appeared in Dr Budd’s classical treatise ‘On Diseases of the Liver;’ and in it the author correctly stated, from data supplied by Mr Busk, that these human flukes were “much thicker and larger than those of the sheep,” being, it is added, from “an inch and a half to near three inches in length.” The longest of my recent specimens, however, scarcely exceeds two inches, whilst the smallest and most perfect (the one at Oxford) measures less than an inch from head to tail. The greatest width of my broadest specimen is little more than half an inch, or 9/16″. None of the twelve examples that I have examined approach the length of three inches; but Mr Busk assured me that, judging from his recollection, some of his specimens were even longer than that. I fear, nevertheless, that the estimate given in my Synopsis is somewhat exaggerated; at all events it is so for average specimens.

Fig. 2.—The large human fluke (Distoma crassum) a, Oral sucker; b, intestine; c, cæcal end of same; d, reproductive papilla; e, uterine rosette (the folds of which are not branched); f, one of the folds (in profile); g, vitellarium; h, hernial protrusion (the result of an injury to the specimen); i, upper testis; j, streaks or layers of seminal fluid which have escaped by rupture and assumed a branched appearance; k, lower testis uninjured (but slightly altered in outline from flattening); l, ventral sucker. Magnified 2 diameters. Original.

The new anatomical facts made out by me bear reference principally to the reproductive apparatus. What else I have observed is for the most part confirmatory of the statements made by Mr Busk. In particular, his brief account of the position and character of the digestive organs was not only confirmed by my earlier examinations, but is now re-verified. In the representation given in my ‘Introduction’ I showed in dotted outline two large organs which I supposed to be the testes. I distinctly observed radiating lines proceeding from the centre in each; but I could not discover the slightest trace of any limiting border to either organ. I now found in the same position two nearly circular flattened masses with clearly defined limits (i, k). No doubt could be entertained as to the testicular character of the lower organ (k). In the original drawing I further indicated the presence of a third and much smaller globular mass, which I termed the ovary; but what I supposed to represent this organ in the particular specimen from which the accompanying illustration was drawn turns out to be merely a hernial protrusion resulting from injury (h). The radiating, broad, and branching seminal ducts are beautifully distinct in one of my specimens, forming the most attractive feature of the parasite’s organisation (k). In consequence of injury to the specimen which is here drawn, the upper testis (i) displays no seminal tubes. I made out the female reproductive organs with more completeness. In the outline drawing given in my introductory treatise I had indicated the probable position of the uterine folds; reducing the organ to the simplest expression of what I concluded must obtain in the normal condition. My conjecture was perfectly correct. The uterus consists of irregularly folded tubes, which, though here and there apparently branching from a central tube, are in reality folded evenly upon themselves. The oviduct can be distinctly traced to its outlet in the reproductive papilla, which, as usual in true Distomes, is placed in the middle line, immediately above the ventral sucker. In my examination of Mr. Busk’s original specimens I could not find the slightest trace of vitelligene organs; but in my fresh examples I not only obtained proof that these organs were largely developed, but that their limitations could be fixed with accuracy (g g). They consisted of two large elongated masses, one on either side of the body, occupying about two thirds of the entire length of the parasite. Their yolk-vesicles were distinctly seen; but the main efferent canals were only here and there traceable. Clearly, the position and character of the yolk-forming glands of this large human fluke are quite unlike those of any of its congeners. This fluke is a remarkably fine species, and, when viewed in the fresh state with a powerful pocket-lens, presents a most striking appearance. I did not observe any cutaneous spines. I found the eggs to present an average long diameter of about 1/200″, by 1/330″ in breadth. They are therefore somewhat smaller than those of the common fluke. In the specimen preserved in the Hunterian Museum there was complete evidence of the presence of an excretory outlet at the caudal extremity; but I did not succeed in finding any trace of the water-vascular system higher up. I have no doubt, however, that it exists.

As regards the affinities of Distoma crassum, it is clear that this Trematode has little in common either with the liver-fluke of cattle and sheep (Fasciola hepatica), or the still larger species obtained by me from the giraffe (Fasciola gigantea). The simple character of the digestive tubes obviously connects it more closely with the lancet-shaped fluke (Distoma lanceolatum), the last-named parasite being, as already shown, an occasional resident in the human liver, where its presence, moreover, undoubtedly contributed towards the production of the fatal result.

In my remarks on the missionary’s diet it is hinted that the Ningpo oysters may have played the rôle of intermediary bearers to the parasite in question; and as tending in some measure to strengthen this notion, it should be borne in mind that Mr. Busk’s original fluke-bearer came from the east. It is not improbable that the Lascar host may have partaken of the same particular species of fish or shell-fish that the missionary and his wife partook of. Be that as it may, the frequency of the occurrence of Trematodes and their larvæ in marine mollusks is well known. According to Woodward, several species of oyster are sold in the Indian and Chinese markets. Thus, it would require the skill of a malacologist to determine the particular species of Ostrea to which the Ningpo oysters should be referred.

Mons. Giard is of opinion that the singular larvæ known as Bucephali attain sexual maturity in sharks and dog-fishes; therefore it is extremely unlikely that the Bucephali should have been in any way concerned in the infection of our missionary and his wife; nevertheless there remains the probability that these human bearers swallowed other kinds of Trematode larvæ when they consumed the Ningpo oysters. Moreover, if it should happen that none of the other larvæ occurring in oysters are capable of developing into flukes in the human territory, it yet remains highly probable that some one or other of the various encysted (and therefore sexually immature) Trematodes known to infest marine fishes will turn out to be the representative of our Distoma crassum. In this connection we must not forget that the flesh of the Salmonidæ forms the probable source of human Bothriocephali; and there is some likelihood that salt-water fishes, if not actually the primary, may become (after the manner explained by M. Giard) the secondary intermediary bearers of fluke-larvæ. At all events, I am inclined to look to the Ningpo oysters, or to some other of the various species of marine shell-fish sold in eastern markets, as the direct source of Distoma crassum; for, in addition to the bucephaloid cercarians, we have abundant evidence of the existence of other and more highly developed fluke-larvæ in marine bivalve mollusks.

In this connection I will only further observe that we possess very little knowledge of the parasites which take up their abode in the viscera of savages. This ignorance results partly from the fact that these untutored races, as proved by the statements of Kaschin and others, actually, in the matter of severe symptoms, suffer much less from the presence of intestinal worms than their civilised fellow-men do. The subject is worthy of further attention, but no one, so far as I am aware, has cared to institute the necessary inquiries in a methodical way. I strongly suspect that several of the human parasites which we now consider to be rare would be found to be abundant if by means of post-mortem examinations and other methods of investigation we could be made acquainted with the facts of helminthism as they occur amongst the raw-flesh and fish-eating savage tribes. Of course any person, notwithstanding the utmost care and cleanliness, as in the cases before us, may contract a noxious parasite; nevertheless, speaking generally, it may be said that the measure of internal parasitism affecting any given class of people bears a strict relation to the degree of barbarism shown by such persons in their choice of food and drink, and in their manner of eating and drinking. This statement, if true, is not destitute of sanitary importance; moreover, it applies not alone to ourselves, but also to all the domesticated animals that serve our wants. Cleanliness is just as necessary for their welfare as for our own.

In the spring of 1878 my patients returned from China. They had experienced fresh attacks from the parasite; moreover, one of their children, a little girl, was also victimised by the same species of fluke. Thus, in one family I have encountered three cases of fluke-helminthiasis due to Distoma crassum! One of the worms passed by the little girl per anum is now in my possession. It not only shows the upper testis perfectly, but also the many times transversely folded, simple, uterine rosette which is certainly not branched. There are also traces of an organ which I take to be the cirrhus-pouch; but I have never seen the penis protruded externally.

For the purposes of diagnosis I subjoin the following characters. The Distoma crassum is a large, flat helminth varying from an inch and a half to two and a half inches in length, and having an average breadth of five eighths of an inch; it is especially also characterised by its uniform and considerable thickness, combined with the presence of a double alimentary canal which is not branched; the body is pointed in front, and obtusely rounded posteriorly; the integument being smooth and unarmed; the reproductive orifices placed immediately above the ventral sucker; the testes form two large rounded organs, situated below the uterine rosette, and disposed in the middle line, one in front of the other; the uterine folds occupy the front part of the body; near the lateral margins there are two large vitelligene glands, one on either side of the intestinal tube; the excretory organ probably consists of a central trunk with diverging branches, opening below.

Bibliography (No. 5).—Budd, original notice in his ‘Diseases of the Liver,’ 2nd edition, quoted by Lankester in Appendix B to Küchenmeister’s ‘Manual of Parasites,’ p. 437, 1857.—Cobbold, T. S., “Synopsis of the Distomidæ,” in ‘Journ. of the Proceed. of the Linnean Soc.,’ vol. v, Zool. Div., 1860 (original description p. 5).—Idem, ‘Entozoa,’ p. 193, 1864.—Idem, “Remarks on the Human Fluke Fauna, with especial reference to recent additions from India and the East,” the ‘Veterinarian,’ April, 1876.—Idem, “On the supposed Rarity, Nomenclature, Structure, Affinities, and Source of the large Human Fluke (D. crassum),” ‘Linn. Soc. Journ.,’ vol. xii, Zool. Div., 1876, p. 285 et seq.—Idem, “Observations on the large Human Fluke, with notes of two cases in which a missionary and his wife were the victims,” the ‘Veterinarian,’ Feb., 1876.—Idem, “The new Human Fluke,” in a letter published in the ‘Lancet,’ Sept., 1875.—Leidy, in ‘Proceed. Acad. Nat. Sciences of Philadelphia;’ see also Dr McConnell’s paper quoted below (Bibl. No. 6).—Leuckart, l. c., Bd. I, s. 560.—Weinland, l. c. (Bibl. No. 2), Appendix, p. 87.

Fig. 3.—The Chinese fluke (Distoma Sinense). a, Oral sucker; b, œsophageal bulb; c, intestine; c′, cæcal end; d, ventral sucker; e, genital pore; f, uterine folds; g, ovary; h, vitellarium; i, vitelligene duct; k, upper seminal reservoir; l, testes; m, lower seminal pouch; o, vas deferens; p, pulsatile vesicle; p′, water vessel. After McConnell.

Distoma Sinense, Cobbold.—The discovery of this species is due to Prof. J. F. P. McConnell, who “on the 9th of Sept., 1874, found a large number of flukes in the liver of a Chinese, obstructing the bile ducts.” The species measures 7/10″ in length, by 1/7″ in breadth, the eggs being 1/833″ by 1/1666″. Dr McConnell showed in his original memoir that the worm cannot well be confounded with Fasciola hepatica, with Distoma lanceolatum, or with D. conjunctum. In this conclusion he was supported by Dr T. R. Lewis, who examined the specimens with him. In a letter communicated to the ‘Lancet,’ quoted above, I proposed the nomenclature here given; but Prof. Leuckart, unaware of this step, afterwards suggested the terms Distomum spatulatum. Later on I received numerous specimens from Calcutta, the examination of which enabled me to confirm the accuracy of the original description. As regards the male organs in the subjoined figure, it will be seen, by comparing the lettering and references, that I have interpreted the facts of structure somewhat differently from Prof. McConnell.

In the month of December, 1874, a Chinese died in the Civil Hospital at Port Louis, Mauritius, whilst he was under the care of Dr William Macgregor, chief medical officer of the Colony of Fiji. The post mortem revealed the presence of a very great number of flukes in the bile-ducts. Dr Macgregor described these parasites with great care, and having favored me with a copy of his manuscript I at once recognised the worms to be identical with the species discovered by McConnell. I also received through Dr Henry Clark, of Glasgow, two Mauritius specimens, which when compared with the Calcutta examples proved to be specifically identical. Dr Macgregor’s paper, communicated to the Glasgow Medico-Chirurgical Society, gives full particulars of the helminthiasis associated with this parasite, whilst both his and Prof. McConnell’s account of the structure of the worm are remarkably complete in details, and well illustrated. It is not a little curious to notice that although these parasites were obtained in countries far removed from China, they were in both instances taken from Chinese; moreover, from the statements of Macgregor, it appears very probable that the parasites in question are a common source of liver disease. Without doubt oriental habits are eminently favorable to fluke infection, for we are now acquainted with four species of flukes whose geographical range is limited to eastern parts.

Bibliography (No. 6).—McConnell, J. F. P., “Remarks on the Anatomy and Pathological relations of a new species of Liver-fluke,” ‘Lancet,’ Aug. 1875; repr. in the ‘Veterinarian,’ Oct., 1875; also in the ‘Lancet,’ March 16th, 1878, p. 406.—Macgregor, W., “A new form of Paralytic Disease, associated with the presence of a new species of Liver Parasite (Distoma Sinense),” ‘Glasgow Med. Journ.’ for Jan., 1877; also in the ‘Lancet’ for May 26th, 1877, p. 775.—Cobbold, T. S., in a note to the ‘Lancet,’ Sept., 1875, and in the Appendix to Macgregor’s paper, p. 15, 1877.—Leuckart, R., l. c., Bd. ii, s. 871, 1876.

Distoma conjunctum, Cobbold.—The little fluke which I first discovered in the gall-ducts of an American fox (Canis fulvus) was fourteen years afterwards obtained from pariah dogs in India by Dr T. R. Lewis (1872); but it remained for Prof. McConnell to show that this entozoon also invades the human subject (1874). A second instance of its occurrence in man was recorded in 1876. We all figured the worm, and in respect of general details our descriptions for the most part agreed (fig. [56]). The worms from the dog and fox gave an average of 1/4″ in length, but the majority of those found by McConnell in man were fully 3/8″ from head to tail.

Writing in the spring of 1876 Dr McConnell says:—“In the ‘Lancet’ for the 21st of August, 1875, I published the description of a new species of liver-fluke found in the bile-ducts of a Chinaman (sic) who died in this hospital. Dr Spencer Cobbold has very kindly interested himself in this discovery, and proposed the name of Distoma Sinense for the new fluke. This discovery (in September, 1874) has stimulated me to pay still greater attention to the morbid conditions of the biliary canals in our post-mortem examinations; but, although more than 500 autopsies have been conducted since that date, I have not met with another instance of distomata in the liver until within the last fortnight. On the 9th of January, 1876, in examining the liver of a native patient who had died in the hospital, I again found a large number of flukes in the bile-ducts, and having carefully examined many specimens, I recognise the species as the D. conjunctum of Cobbold. Dr Cobbold discovered this fluke in 1858; but, as far as I am aware, the human liver has never hitherto been found infested by these parasites, and this will give general interest and importance to the following case.”

“Jamalli Khan, a Mahommedan, aged twenty-four, admitted into the hospital on the 25th of December, 1875. He is a resident of Calcutta, and an ordinary labourer (coolie). He states that he had been suffering from ‘fever’ for the last two months, at first intermittent in character, but for the last seven days more or less continued. He is much emaciated and reduced in strength. Complains of pain on pressure over the liver and spleen; the latter can be felt much enlarged, reaching downwards to nearly the level of the umbilicus; the lower border of the liver, however, can only just be felt below the ribs. Temperature on evening of admission 101° F. Conjunctivæ are anæmic, but not jaundiced. Has also a little bronchitis. The fever continued with slight remissions for ten days (January 4th, 1876), the highest diurnal temperature (in the afternoon) varying from 103° to 104° F.; it then abated, but dysentery set in. He began to pass six or eight stools in the twenty-four hours, attended with much griping, and containing varying quantities of blood-tinged, gelatinous mucus. These became more frequent, in spite of treatment, during the next three days, and on the 8th of January he was manifestly sinking; passed his evacuations into the bedclothes, became cold and collapsed, and died in this state that same evening.

“A post-mortem examination was made on the following morning, thirteen hours after death. All the organs of the body were found more or less anæmic, but exhibited nothing remarkable with the following exceptions. The lungs towards their posterior margins and bases were dark, but still spongy and crepitant. The spleen was found greatly enlarged, heavy; capsule tense and stretched; substance soft, reddish brown, irregularly pigmented; weight 1 lb. 13 oz. The liver was of about normal size; its surfaces smooth, the capsule slightly hazy looking. Hepatic substance firm, but abnormally dark, and the bile-ducts particularly prominent and thickened. Numbers of small distomata escaped from the incisions made into the organ, and could be seen protruding from the dilated biliary canals. The gall-bladder was filled with thick greenish-yellow bile, measuring about an ounce and a half, but containing no parasites, and no ova even could be detected on microscopical examination of this bile and of scrapings from the lining membrane of the gall-bladder. The cystic duct was free from obstruction. The condition of the common choledic duct could not so well be ascertained, as the liver had been removed from the abdominal cavity before anything extraordinary had been detected in its condition, but, so far as it could be examined, it was found patent; the duodenal mucous membrane was well bile-stained, and there was evidence of biliary colouring matter in the fæcal contents of the bowels. On carefully dissecting out, and then laying open, the biliary ducts in a portion of the right lobe of the liver (the rest being preserved entire), numbers of distomata were found within them, lying singly, flattened, and generally with the anterior extremity, or “oral sucker,” directed towards the periphery of the organ, the posterior extremity towards its centre; or in twos, threes, or even little groups of fours, variously coiled upon themselves or upon each other. The lining membrane of the biliary canals was found abnormally vascular, its epithelial contents abundant (catarrh?), and, among these, ova could be detected under the microscope. Sections of the liver, hardened and then examined in glycerine, showed fatty infiltration of the lobular structure, but not to any advanced degree; the bile ducts considerably dilated, their walls thick and hypertrophied, but nothing else abnormal, or in any way remarkable. The weight of the liver was 3 lbs. In the transverse and descending colon numerous indolent-looking, shallow, pigmented ulcers were found, and in the rectum others evidently more recent and highly injected. The submucous tissues throughout were abnormally thickened. The intestinal contents consisted of only about three ounces of thin yellowish (bilious) fæcal fluid, with small bits of opaque mucus. This was carefully washed and examined, but no flukes were discovered. About a dozen distomata escaped from the liver on making the primary incisions, and quite twice this number was found subsequently within the biliary canals. Only a portion of the right lobe has, as I have said, been dissected, so that it may be confidently stated that probably not less than a hundred of these flukes must have infested this liver. All were found dead, but it must be remembered that the autopsy was performed thirteen hours after the death of the patient. It is remarkable that in this case, as in the one before described by me, no distomata were found in the gall-bladder. The presence of these parasites in the bile-ducts seems to have led to catarrhal inflammation of their lining membrane and abnormal thickening and dilatation of their walls, but there is no evidence of their having caused sufficient obstruction to produce cholæmia, as in the case just referred to, and no marked pathological change could be detected in the lobular structure of the liver.”

After referring to the anatomical descriptions of the worm, as recorded by myself (in ‘Entozoa’) and by Lewis (in the memoir quoted below), Professor McConnell further observes that the addition of a few more particulars seems necessary for the determination of the identity of the species. He then gives the following characters:

“Body lanceolate, anterior and posterior extremities pointed, the latter obtusely. Surface covered with minute spines or hairs. Average length 3/8″ (three eighths of an inch); average breadth 1/10″. ‘Ventral’ sucker slightly smaller than ‘oral.’ Reproductive papilla or genital orifice placed a little above and to one side of the former. Alimentary canal double and unbranched. Uterine folds and ovary placed in the median line, and above the male generative organs, the latter consisting of two very distinct globular bodies or testes. Ova of the usual type, i.e. oval in outline, having a double contour, and granular contents; average length, 1/750″; average breadth, 1/1333″. The only point of note is that the average length of these flukes is greater than that of the same species found by the authors above referred to. The D. conjunctum in the American fox, and in the pariah dog, has an average length of 1/4″; only two or three specimens of this size were found in this liver, and these showed evidences of immaturity; a few were found 1/2″ in length; but the great majority exactly 3/8″. The anatomical characters are otherwise precisely identical.”

Professor McConnell concludes his communication by a remark in reference to the common source of infection shared by mankind and dogs in India. The occurrence, however, of this entozoon in an American red fox points to a very wide geographical distribution of the species. It is hardly likely that the fox, though dying in the London Zoological Society’s Menagerie, should have contracted the parasite in England. In the second half of this work I shall reproduce my original drawing (fig. [56]) from the ‘Linnean Transactions;’ but I may refer to my Manual (quoted below) for a reproduction of McConnell’s figure. In my original specimens the integumentary spines had fallen, probably as a result of post-mortem decomposition.

Bibliography (No. 7).—Cobbold, T. S., “Synopsis of the Distomidæ,” (l. c.), 1859; and in “Further Observations on Entozoa, with experiments,” ‘Linn. Trans.,’ vol. xxiii (tab. 33, p. 349), 1860.—Idem, “List of Entozoa, including Pentastomes, from animals dying at the Zool. Soc. Menagerie between the years 1857–60,” ‘Proceed. Zool. Soc.,’ 1861.—Idem, ‘Entozoa,’ p. 20, pl. ii, 1864; and in “Manual of the Internal Parasites of our Domesticated Animals,” p. 81, 1873.—Lewis, T. R., and Cunningham, D. D., in a footnote to their ‘Microscopical and Physiological Researches,’ Appendix C., ‘Eighth Ann. Rep. of the San. Comm. with the Govt. of India,’ p. 168, Calcutta, 1872.—McConnell, J. F. P., “On the Distoma conjunctum,” in the ‘Lancet’ for 1875–76, quoted above; reprinted in the ‘Veterinarian,’ 1876; also (a second case) in the ‘Lancet’ for March 30th, 1878, p. 476.

Fig. 4.—The small Egyp­tian fluke (Dis­to­ma het­ero­phy­es), viewed from behind. The large ven­tral suck­er, sup­ple­men­tary disk, uterus, testes, simple divided in­tes­tine, vi­tel­lar­ium, and pul­sa­tile ve­si­cle are con­spicu­ous. Original.

Distoma heterophyes, Von Siebold.—This minute parasite, measuring only 3/4 of a line in length, was discovered by Dr Bilharz, of Cairo, in the intestines of a lad, post-mortem, in the year 1851. A second similar instance occurred, when several hundred examples were collected and afterwards distributed amongst the helminthologists of Europe. Through the kindness of Leuckart two of the worms eventually reached myself. From one of these the accompanying figure was drawn. For the purpose of supplying a full diagnosis I have elsewhere described this worm as presenting an oblong, pyriform outline, attenuated in front, and obtusely rounded behind; body compressed throughout, the surface being armed with numerous minute spines, which are particularly conspicuous (under the microscope) towards the head; oral and ventral suckers largely developed, the latter being near the centre of the body, and about twice the diameter of the former; pharyngeal bulb distinct and separate from the oral sucker, and continued into a long œsophagus, which divides immediately above the ventral acetabulum; intestinal tubes simple, gradually widening below and terminating near the posterior end of the body; reproductive orifices inconspicuous, but evidently placed below and a little to the right of the ventral sucker, at which point they are surrounded by a special accessory organ, resembling a supernumerary sucker; uterine folds numerous and communicating with small but conspicuously developed vitelligene glands; testes spherical and placed on the same level in the lower part of the body; ovary distinct; aquiferous system terminating inferiorly in a large oval contractile vesicle, the latter opening externally by a central foramen caudale.

Apart from its minuteness, moreover, this trematode is especially characterised by the possession of a very remarkable apparatus surrounding the reproductive orifices. It consists of an irregularly circular disk, measuring 1/125″ in diameter, and having a thick-lipped margin, which supports seventy fish- basket-like horny ribs comparable to the claw-formations seen in the genus Octobothrium. According to Bilharz these ribs give off five little branches from their sides, but Leuckart could not see them in his specimens. Leuckart estimated the length of these horny filaments to be 1/1250″, whilst their breadth was 1/3570″. On the whole we may regard this organ as a complicated form of “holdfast” designed to facilitate or give efficiency to the sexual act. I may here also state that this structure is by no means unique; for, if I mistake not, it exists in an equally developed degree in the young trematode which Dr Leared found infesting the heart of a turtle. Leared believed that he had found an ordinary distome; an opinion to which I could not give my assent, seeing that the organ described by him as a “folded, ventral sucker” presented a very different aspect to the oral sucker displayed by the same animal. Without doubt, however, the organ in his so-called Distoma constrictum is analogous to the supplementary “holdfast” existing in Distoma heterophyes. The views which I originally advanced as to the source and condition of the parasite are probably correct.

As regards the structure of Distoma heterophyes, I have only to add that a special set of glandular organs is situated on either side of the elongated œsophagus, but the connection between these organs and the digestive apparatus has not been clearly made out. Leuckart compares them to the so-called salivary glands found in Distoma lanceolatum, and says, “The presence of such a glandular apparatus is also indicated by the more ventral position of the oral sucker, and the development of the cephalic margin.” The conspicuous contractile vesicle terminating the excretory system is developed to an unusually large extent, exhibiting in its interior multitudes of the well-known active molecular particles. Lastly, I have only to add that the eggs of Distoma heterophyes measure 1/990″ in length by 1/666″ transversely.

Fig. 5.—The eye fluke (Dis­to­ma oph­thal­mo­bi­um). Show­ing the suck­ers and in­tes­ti­nal tubes. Af­ter Von Am­mon.

Bibliography (No. 8).—Bilharz, “Beitrag zur Helminth. humana,” ‘Zeitsch. für wissenschaftl. Zool.,’ s. 62, 1851.—Cobbold, ‘Entozoa,’ p. 195, 1864.—Küchenmeister, F., ‘Parasiten,’ 1855, s. 210, Eng. edit., p. 276, 1857.—Leared, “Description of Distoma constrictum,” ‘Quarterly Journal of Micros. Science,’ new series, vol. ii, 1862.—Leuckart, R., l. c., s. 613, 1863.—Moquin-Tandon, on the Genus Fasciola, l. c., 1861.—Weinland, on Dicrocœlium, l. c., p. 86, 1858.

Distoma ophthalmobium, Diesing.—There is every reason to believe that the small flukes found by Gescheid and Von Ammon in the human eye were sexually immature worms, but since it cannot be decided as to what adult species they are referable I prefer to notice them under the usual title. Possibly these eye-worms may be referred to D. lanceolatum, as suggested by Leuckart. However that may be, I deem it unnecessary to repeat the details recorded in the treatises quoted below. The largest examples measured only half a line or about one millimètre in length.

Bibliography (No. 9).—Cobbold, ‘Entozoa,’ p. 191.—Gescheid (D. oculi humani), in Von Ammon’s ‘Zeitsch. f. Ophth.,’ iii, and also in Ammon’s ‘Klin. Darstell. d. Krankheit d. Menschl. Auges.,’ vols. i and iii.—Küchenmeister, Eng. edit., p. 287.—Leuckart, l. c., s. 610.—Nordmann (Monostoma lentis), “Mikr. Beitr.,” Heft. ii, ‘Vorwort,’ s. ix, 1832.

Tetrastoma renale, Chiaje; Hexathyridium pinguicola, Treutler; and H. venarum, Treutler.—Whether these forms are good species or not, the fact that they were genuine parasites cannot, I think, be disputed. The first-mentioned measured five lines in length, and was found by Lucarelli in the urine. The second, eight lines long, was found by Treutler in a small tumour connected with the ovary. The third, measuring three lines in length, was twice found in venous blood, and twice in the sputum of patients suffering from hæmoptysis.

Bibliography (No. 10).—Delle-Chiaje, ‘Elmintografia Umana,’ 1833.—Bremser (l. c., Bibl. No. 2), s. 265, 1819.—Cobbold, ‘Entozoa’ (p. 204, et seq.).—Dujardin (l. c., Bibl. No. 2), s. 265, 1819.—Treutler, ‘Obs. Path. Anat. ad Helm. Corp. Humani,’ p. 19, 1793.—Zeder, ‘Anleitung zur Naturg. der Eingeweidewürmer,’ s. 230, 1803.

Amphistoma hominis, Lewis, and McConnell.—The original account of this species is based upon two finds. The first series of specimens was procured from Dr J. O’Brien, of Gowhatty, and the second set from the Pathological Museum of the Calcutta Medical College. Dr O’Brien and Dr Curran together procured their specimens, post-mortem, from an Assamese. There were hundreds of worms present in the vicinity of the ileo-colic valve. The museum specimens were procured from a patient who died at the Tirhoot gaol hospital in 1857. They were (say the authors) presented to the museum by Dr Simpson, and in the catalogue their history was briefly recorded as follows:

Fig. 6.—The human amphistome (Amphistoma hominis). Longitudinal section. a, Oral sucker; b, pharyngeal bulb; c, nerve ganglia; d, œsophagus; e, genital pore; f, vagina; g, ductus ejaculatorius; h, ventral nerve cords; i, intestinal canal; j, upper testis; k, water vessel; l, lower testis (ovary according to Lewis); m, principal ducts of the vitellarium; n, branches of the vitellary ducts; o, ventral pouch or bursa; p, caudal sucker. Magnified 12 diameters. After Lewis.

“The cæcum of a native prisoner who died from cholera in the Tirhoot gaol hospital, with a number of peculiar and, probably, hitherto unrecognised parasites, found alive in that part of the intestinal canal.” (Presented by Dr Simpson through Professor E. Goodeve.)

In continuation of their narrative, Drs Lewis and McConnell go on to say that, “with reference to this preparation, the following very interesting particulars from the ‘Annual Jail Report of Tirhoot’ for 1857 have been very kindly placed at our disposal by the Surgeon-General, Indian Medical Department. The prisoner, Singhesur Doradh, aged 30, was attacked with cholera on the 13th, and died on the 14th of July, 1857. Had not been in hospital previously, and was employed in cleaning the jail.”

The post-mortem examination was made three hours after death:—“Colon externally livid, contracted; contains a little serous fluid with flakes of mucus. Mucous membrane healthy except venous injection. In the cæcum and ascending colon numerous parasites like tadpoles, alive, adhering to the mucous membrane by their mouths. The mucous membrane marked with numerous red spots like leech-bites from these parasites. The parasites found only in the cæcum and ascending colon, none in the small intestines.” This description is by Dr Simpson, who adds, “I have never seen such parasites, and apparently they are unknown to the natives. They are of a red colour, size of a tadpole, some young, others apparently full grown, alive, adhering to mucous membrane,—head round, with circular open mouth, which they had the power of dilating and contracting. Body short and tapering to a blunt point.”

Drs Lewis and McConnell’s description of the worm is too long to be quoted in full. The parasites measure 1/5″ to 1/3″ in length, by 1/8″ to 1/6″ in breadth. Science is much indebted to these eminent observers for having unearthed the museum specimens and for recording the facts they could gather. From a zoological point of view the most interesting fact connected with Lewis’s amphistome is the existence of a gastric pouch. This structure brings these human Masuri into close relation with the equine parasite which I have named Gastrodiscus Sonsinoii, and which will be found illustrated in this work (fig. [62]). In short, Lewis’s worm appears like a transition form; the absence of gastric supplementary suckerlets separating it from the new generic type.

Bibliography (No. 11).—Lewis, T. R., and McConnell, T. F. P., “Amph. hominis; a new parasite affecting Man,” ‘Proceedings of the Asiatic Society of Bengal,’ Aug., 1876.

Bilharzia hæmatobia, Cobbold.—This remarkable parasite was discovered by Bilharz in 1851. It was subsequently found by myself in an ape (1857); other species of the same genus having since been detected by Sonsino in the ox and sheep (1876). The human examples were originally obtained from the portal system of blood-vessels. Afterwards they were obtained by Bilharz, Griesinger, and others, from the veins of the mesentery and bladder. It was shown that they were not only associated with, but actually gave rise to a formidable and very common disease in Egypt.

In 1864 Dr John Harley made the interesting announcement that he had discovered specimens of this singular genus in a patient from the Cape of Good Hope. He also showed that the entozoon was the cause of the hæmaturia known to be endemic at the Cape. Harley believed his parasites to represent a new species (Distoma capense), but in this view I showed that he was mistaken. His admirable contribution, nevertheless, served not only to establish the wide range of this parasite on the African continent, but also to throw much light upon the subject of endemic helminthiasis. As this worm forms an almost altogether exceptional type of fluke-structure, it became necessary to supersede the original nomenclature proposed by Bilharz and Von Siebold (Distoma hæmatobium). Accordingly I proposed the term Bilharzia, whilst other helminthologists subsequently proposed various titles (Gynæcophorus, Diesing; Schistosoma, Weinland; Thecosoma, Moquin-Tandon). On various grounds, and chiefly on account of priority, most writers have at length definitely accepted the nomenclature which employed the discoverer’s name for generic recognition.

Fig. 7.—The blood fluke (Bil­har­zia hæma­to­bia). The lower end of the fe­male is with­drawn from the gy­næ­co­pho­ric ca­nal of the male. Af­ter Kü­chen­mei­ster.

The Bilharzia hæmatobia may be described as a trematode helminth in which the male and female reproductive organs occur in separate individuals; the male being a cylindrical vermiform worm, measuring only half an inch or rather more in length, whilst the female is filiform, longer, and much narrower than the male, being about four fifths of an inch from head to tail; in both, the oral and ventral suckers are placed near each other at the front of the body; in the male the suckers measuring 1/100″, in the female 1/314″ in diameter; in either, the reproductive orifice occurs immediately below the ventral acetabulum. The comparatively short, thick, and flattened body of the male is tuberculated and furnished with a gynæcophoric canal, extending from a point a little below the ventral sucker to the extremity of the tail; this slit-like cavity being formed by the narrowing and bending inwards of the lateral borders of the animal, the right side being more or less completely overlapped by the left margin of the body; caudal extremity pointed; intestine in the form of two simple blind canals. Female with a cylindrical body measuring only 1/312″ of an inch in thickness in front of the oral sucker; lodged in the gynæcophoric canal of the male during the copulatory act; thickness of the body below the ventral acetabulum being about 1/357″, and at the lower part 1/96″; surface almost smooth throughout; intestinal canals reunited after a short separation to form a broad, central, spirally twisted tube extending down the middle of the body; vitelligene and germigene canals combining to form a simple oviducal canal, which is continued into a simple uterine tube, finally opening near the lower margin of the ventral sucker; eggs pointed at one end, or furnished with a projecting spine near the hinder pole.

Fig. 8.—Two eggs of Bilharzia. a, With the yolk coarsely segmented; b, with the yolk granulated and the spine wanting. Original.

The study of the structure and formation of the contents of the ova possesses great interest. When fully developed the eggs are oval, measuring from 1/180″ to 1/160″ in length, with an average transverse diameter of 1/325″. Some are a trifle larger, others smaller. Occasionally one encounters narrow specimens, and also aberrant forms presenting a pear-shaped outline. I have met with eggs not exceeding 1/250″ in their long diameter, and 1/500″ transversely, whose yolk-contents had already arrived at an advanced stage of segmentation.

The shell is transparent, of a brown colour, and free from any markings, lines, or sculpturing. One pole of the shell is invariably narrower than the other, and usually presents a more or less pointed extremity (fig. 8). This narrow end commonly displays a sharp, projecting, beak-like spine, which, at its base, constantly rests upon the centre of the pole of the shell, but occasionally it is eccentrically placed (fig. 8a). In some few examples the spine is removed to a little distance from the actual extremity of the shell; but even in these instances, so far as my observations go, its apex always projects beyond the level of the curved end of the pole. Now and then the spine is altogether absent (fig. 8b); and when present it is, as already hinted, very unequally developed. In size the spine ranges from a mere point, having an extreme length of only 1/8000″, up to the comparatively large magnitude of 1/2500″ lengthways.

According to the best evidence there is no good ground for asserting the existence of any specific differentiation between the parasites coming from the Cape and Egypt respectively.

Fig. 9.—Two eggs of Bilharzia, with eccentrically placed spines. That to the left shows mulberry cleavage of the yolk; the other having lost its embryonal contents by rupture. Original.

Taking a more extended view of the significance of these singular chorional spines, I think we may here recognise the early efforts of Nature, so to speak, to form or evolve a special organ, which, in the eggs of certain other parasites, becomes capable of attaining a relatively prodigious degree of development. To me it seems that the little process in question is a kind of rudimentary holdfast; and, as such, it may be reckoned as the homologue of a variety of egg-appendages. Eleven years ago Mr Edwin Canton discovered some curious ova attached to the conjunctiva of a turtle’s eye. I had no hesitation in pronouncing them to be referable to some ectozoon or entozoon belonging to one or other of the allied genera Polystoma, Tristoma, Octobothrium, and Dactylogyrus. Now, whilst the Bilharzia ova display only a solitary and imperfectly developed holdfast, placed at one end of the shell, the singular eggs described by Mr Canton develop organs of anchorage at both extremities. Parasitic ova exhibiting analogous processes, spines, and filamentary appendages at both poles, have been observed in various species of parasite—as, for example, in Monostoma verrucosum infesting the fox, in Tænia cyathiformis infesting the swallow, in Tænia variabilis of the gambet, in Octobothrium lanceolatum attached to the gills of the common herring; and in Polystoma appendiculata, from the branchiæ of various marine fishes. Eggs of parasites which, like Bilharzia, are furnished with a single appendage, may likewise be seen in the ova of different species of Dactylogyrus infesting the gills of the pike. In the more strongly pronounced developments it is easy to perceive how admirably these outgrowths are adapted to the necessities of the different species of parasite to which they are severally referable; and, even in the case of Bilharzia, the trifling amount of anchorage furnished by a projecting point is not absolutely thrown away. The resistance will also be greater where the spine is situated a little on one side of the pole of the egg, which seems to need steadying during the violent struggles of the embryo to escape from its temporary abode.

When any number of ova are removed from the urine and examined, it will be found that a large proportion of them contain embryos in an advanced stage of larval growth. The structural appearances presented by the embryos whilst still in the eggs are remarkably uniform; since, in all, the yolk appears to have resolved itself into a mass of rounded sarcode-globules, one or two of these particles being conspicuously larger than the rest (fig. [12]). At this stage, except towards the cephalic division of the larva, no tendency to differentiation is perceptible; but some time after the embryo has escaped, one may notice elongated masses of sarcode formed by the coalescence of the globules. Whilst still in the egg, one end of the primitive embryonal mass becomes gradually narrowed, cilia at the same time appearing. This part becomes the future head, eventually acquiring the form of a cowl. Whatever form the body of the embryo may display after extrusion from the shell, the head retains its conical shape, the cone itself being narrowed or widened only when the larva is subjected to abnormal conditions (fig. [14]). Whilst the head is undergoing development within the shell, one, two, or sometimes three, pyriform masses make their appearance within the cone; and after the embryo has escaped, these structures become more marked (fig. 10). The sarcode-globules refract light strongly; and, when the larva is not compressed in any way, they move freely within the somatic cavity. In well-developed embryos, whilst still in the egg, the cilia are observed to clothe every part of the larva except the oral papilla. This minute nipple-like projection measures about the 1/3000 of an inch transversely, forming a very simple kind of unarmed proboscis. When the head of the free embryo is viewed from above, the proboscis looks like a central ring surrounded by a series of regular folds, which radiate outwards like the spokes of a wheel. The ridges thus formed support numerous cilia, these latter projecting at the circumferential margin of the cephalic cone in such a way as to present the figure of a star. Dr Harley has admirably represented this character, which is shared by many other parasitic larvæ. Throughout the greater part of the time, whilst the embryo is still resident within the egg, the broad neck or base of the cephalic cone forms a fixed point of resistance by its firm attachment to the inner wall of the shell; and this structural union, so long as it remains intact, enables the embryo to move not only its head and body from side to side synchronously, but also each part independently. When the time for final escape is drawing near, the vigorous movements of the cone-shaped head seem chiefly concerned in loosening the membranous connection just referred to; and when, at length, the ciliated animalcule has succeeded in overcoming this first difficulty, it is ludicrous to witness its frantic efforts to find an opening in the shell. While thus partially liberated, it will rush to and fro from one pole of the egg to the other, performing a series of summersaults, and at the same time occasionally rolling itself over laterally. This activity becomes gradually more and more violent, until at length its excitement is worked up into a sort of frenzy. I have many times watched these performances, which, however, are only to be seen within those ova whose shells, for some reason or other, refuse to yield to the earlier and ordinary efforts of the prisoner. In all cases where these phenomena are witnessed the eye readily detects a number of small free globules between the embryo and the inner wall of the shell (fig. [13]). These minute particles are likewise tossed about tumultuously during the rapid rotatory movements of the imprisoned larva. Except as regards their size, these globules do not differ in character from the sarcodic contents of the animalcule. They are probably superfluous detachments from the primitive yolk-mass, but it is possible that they may afford some aid in the final breaking up of the shell. Whilst the embryo remains fixed its tail is usually directed towards the narrower or spine-bearing pole of the egg, but in a few instances I have seen this position reversed. As regards the precise mode of emerging from the shell, and the time occupied by the larva in freeing itself, there are several points of interest. Speaking generally, the purer the medium into which the ova are transferred, the more rapid will be the movements of the larvæ. To give an example of observed facts in relation to the rapidity of development, I cite the following:—“On the 20th of August, 1870, I placed twelve eggs of Bilharzia under the microscope. The medium in which they were immersed consisted of eight parts of ordinary drinking water to one of urine. At the expiration of seventeen minutes the first-born made its escape. In the course of another minute two more emerged. In twenty-six minutes the fourth, in twenty-eight the fifth, in thirty-two the sixth, in thirty-four the seventh, in thirty-seven the eighth, in thirty-eight the ninth, in forty the tenth, in forty-three the eleventh, and in forty-six minutes the twelfth, respectively made their appearance.”

Now, this rapid mode of birth and emergence from the shell is very much more striking in the case of eggs which are placed in perfectly pure water; for, whilst the eggs are still in the urine, there appears to be neither the power nor the inclination on the part of the embryo to escape; but, on isolating and placing them in suitable conditions, their behaviour is even more remarkable. In a space of less than two minutes I have repeatedly seen the hitherto motionless embryo alter its shape by contractions, become violently agitated, and burst out of its shell in the condition of a free-swimming animalcule. Moreover, it is worthy of remark that the eggs and larvæ of Bilharzia soon perish in stale urine. “On the 16th of August, 1870, I placed about a thousand eggs in a quart of fountain-water, to which only a drachm or rather less of urine had been added. At the expiration of forty-eight hours not a single living embryo could be found. I subsequently ascertained that I could not keep the embryos alive for twenty-four hours in any water in which I had introduced the smallest trace of mucus, blood-corpuscles, urinary crystals, or decomposing matters of any kind. All sorts of reagents speedily killed the larvæ. Mere discoloration by carmine solution, or by the addition of a drop of the solution of permanganate of potash, instantly caused them to assume grotesque and unnatural shapes (figs. 13 and 14), death sooner or later following as a result of the disintegration and resolution of their delicate bodies into mere sarcode-masses. Still more rapidly poisonous effects were produced by the addition of a little sherry or alcohol. In solutions where the amount of spirit did not exceed one part of spirit, proof strength, to fifty parts of water the effect was the same.”

The development of the larva is equally well accomplished in distilled water, in well-water, and in brackish water. In pure sea-water the process goes on less satisfactorily. It was found, indeed, that the addition of slightly saline water to ciliated embryos, which were on the point of expiring in fresh water, had the effect of reviving them for a time. These facts have an important practical bearing.

I have thus shown that the escape of the embryo is by no means the slow process that Bilharz has described. Almost invariably the shell bursts by a longitudinal slit extending over fully two thirds of its long diameter, the first point of rupture being commonly situated midway between the spine and the centre of the shell. In normal births, so to speak, the head of the animalcule emerges first; but occasionally the animal escapes sideways, and I have even seen the embryo extricate itself tail foremost. Not unfrequently it has a difficulty in detaching itself from the shell, in which case the egg is whirled round and round by the half-freed prisoner (fig. [15]). The lodgment of the spine, however, against any foreign substance affords the necessary leverage for ensuring escape.

The larva never displays its proper elongated, spindle-shaped, or cylindro-conical figure, until some short time after its escape from the shell; and, as a consequence of this, its powers of locomotion are less marked at first than they are subsequently. At the time of extrusion the larvæ are commonly more or less hour-glass shaped (fig. [11]); this particular form being sometimes retained for many minutes or even for an hour. Usually the larvæ have a tendency to acquire their normal shape immediately after quitting the shell; the oval, pear-shaped, and variously contracted forms gradually merging into the characteristic cone-shaped animalcule (fig. [10]). In their fully developed condition, they exhibit the most lively movements; and to witness several hundreds of them rushing about with unceasing activity is a curious sight. The phenomenon, moreover, loses none of its interest from the consideration that only a few hours, or it may have been minutes, previously, these now actively gyrating animalcules were lodged in ovo within the blood-vessels of their human host. From persons who are infested, myriads of these eggs of Bilharzia daily make their escape during the act of micturition; and, when this act is accomplished by the host out-of-doors, it is easy to perceive how readily the ova may be subjected to conditions favorable to the development of larvæ. The direct passage of the urine into any considerable receptacle of natural or fresh water would in a few minutes ensure the hatching of all the eggs; and in the absence of any such direct aid to development, the accidental occurrence of a shower of rain would, in all localities where the Bilharzia disease is endemic, readily transfer the ova into ditches, ponds, rivers, lakes, and ultimately, perhaps, even into the sea itself.

The behaviour of the embryo under the action of reagents of various kinds is remarkable. Thus, when on the 5th of Sept., 1870, I placed some ova in brackish water, of the strength of two parts of fresh water to one of pure sea-water, their contents were readily developed, though the escaping embryos did not swim vigorously. When again I placed some other eggs in pure sea-water, their contained embryos became instantly transfixed, the vibratile cilia of the head being rigid and motionless. At first I naturally concluded that the embryos were killed outright; but, to my great surprise, the shock passed away in about half an hour, when they revived and were soon afterwards hatched. One of the larvæ thus set free carried off several of the loose intra-chorional globules which had, during the period of transfixion, become firmly adherent to the ends of the caudal cilia. Here I may remark upon a decided difference observable between the cilia of the head and body respectively. The former are at all times vibratile, active, and conspicuous, whilst the latter are more delicate, capable of comparatively little motion, and partaking more of the character of fine setæ. In length their general measurement varies from 1/2500″ to 1/2000″. The action of pure sea-water on the free animalcules, previously immersed in fresh or brackish water, was equally striking. All, without exception, immediately became paralysed and almost motionless; nevertheless, on again adding fresh water, several entirely recovered. It is worthy of notice that in these cases the cephalic cilia furnished the first indications of returning viability. I was particularly struck with the behaviour of one embryo, which, under the stimulus of the sudden shock, retracted its cone-shaped head almost entirely within the general cavity of the body (fig. [14], lower specimen). In their moribund condition, whatever shape the embryo retained, the sarcodic contents gradually faded away; the outline of the creature, however, becoming more marked (fig. [16]). Usually the body of the animalcule became elongated whilst expiring in sea-water. Under other circumstances the embryo frequently bursts; the sarcodic contents escaping in the form of amœba-like bodies and the cilia retaining their powers of movement long after all traces of the sarcode have disappeared.

Fig. 17.—Cili­a­ted em­bryo of Fa­sci­o­la he­pa­tica, show­ing the so-​called eye-spot. After Leuc­kart.

The larvæ of Bilharzia closely resemble those of Fasciola hepatica, which latter may be appropriately noticed in this place. The ciliated embryo of the common liver fluke has the form of a long cone inverted; the anterior end or head being flatly convex. In the centre is a short proboscis-like papilla destitute of cilia (fig. 17). The general covering of cilia rests on a well-defined granular epidermis; this latter being succeeded by a dense peripheral layer of large nucleated cells, each of them measuring about 1/2500″ in diameter. The epidermis measures 1/6250″ in thickness. In the central mass of parenchyma no internal organs are recognisable, but Leuckart observed indications of a canal which he thought might open at the tail, though the opening itself was not actually visible.

As long as the ciliated covering remains intact the embryo, like other animalcules, displays great activity, whirling round and round on its own axis, and also describing gyrations and circles of different degrees of range in the water, the latter movements being accomplished by bending the body upon itself to a greater or lesser curvature. The embryos of Bilharzia and other infusoria exhibit the same behaviour, and, as Leuckart observes, when these embryos knock against any obstruction, they pause after the blow, as if to consider the nature of the substance they have touched. As in the case of fluke embryos generally, the ciliated covering eventually falls off and the embryo reassumes a more or less oval figure, at the same time changing its swimming mode of progression for the less dignified method of creeping. In the free ciliated condition the embryo of the common liver-fluke measures, according to Leuckart, 1/190″ in length, the anterior broad end being 1/500″. The cilia have a longitudinal measurement of 1/1388″.

Fig. 18.—‌Cili­ated em­bryo of Dis­toma lan­ce­o­la­tum. After Leuckart.

According to the observations of Dr Willemoes-Suhm, the cilia of the embryos of the Distoma megastoma are limited to the anterior pole of the body. This is also the arrangement, as Leuckart first pointed out, in Distoma lanceolatum (fig. 18). On the other hand, Pagenstecher has shown that the embryos of Distoma cygnoides and Amphistoma (Diplodiscus) subclavatum are ciliated all over, an observation which, as regards the latter species, has been confirmed by Wagener and others. Dr Pagenstecher’s original statement to the effect that “intrachorional germs of trematodes offer no distinctive characters,” must, therefore, in the present state of our knowledge, be accepted as a general conclusion admitting of many exceptions. In the early stages of development the embryo of Distoma lanceolatum occupies the centre of the egg, and according to Leuckart has its conical head invariably directed towards the upper pole of the shell, or, in other words, to that end of the egg which is furnished with a lid-like operculum. Leuckart describes the embryo itself as “finely granular and armed at the tip with a dagger-like spine, which, with the simultaneous displacement of the adjacent granular mass, can be pushed forward and drawn back again.” Besides this so-called cephalic granular mass, there are within the embryonic body two other granular masses widely separated from each other, but occupying the posterior half of the embryo. These Leuckart supposes to be the rudiments of a future brood, to be developed at the time when the free embryo shall have lost its ciliated swimming apparatus, shall have bored its way by means of the cephalic spine into the tissues of a mollusk, and shall have become metamorphosed into a sac-like larva (Nurse, Sporocyst, or Redia, as the case may be). Whatever be the full significance of these internal developments, we have at least satisfactory evidence that the complete and free embryo is a globe-shaped animalcule, having the anterior third or cephalic end of the body covered with cilia, and armed with a central boring spine. In consequence of this limitation of the ciliated covering, its swimming movements are less vivacious than those of the embryo of Fasciola hepatica; it will, therefore, probably take up its residence in a less active host than that chosen by the embryo of Fasciola, selecting one of those mollusks which either move slowly or are prone to keep at the bottom of the water. The mature eggs have a length of 1/625 to 1/555 of an inch, and a breadth of 1/833″. The long diameter of the free embryo varies from 1/990″ to 1/833″, the transverse diameter being 1/1562″. Whilst the embryos were still in the egg Leuckart could see no ciliary motion. With most observers, both the ciliary apparatus and the boring spine appear at this stage to have altogether escaped observation.

Fig. 19.—Outline rep­re­sen­ta­tion of a cil­iated embryo of Bil­harzia, show­ing the arrange­ment of the water vessels and the vacuoles. Original.

As regards the intimate structure of the ciliated embryo of Bilharzia hæmatobia, I have further to observe that, shortly after its extrusion from the shell, the hitherto loose, globular sarcode particles coalesce. This is apparently a preliminary step towards the subsequent differentiation process. Respecting the pedunculated blind sacs formed within the head, I think that we must regard the largest one as representing the stomach of the larva in its future cercarian stage. Under the 1/12″ objective I distinctly recognised, in the cavity of the central blind sac, numerous highly refracting granules, the diameter of which averaged not more than 1/12000″. The rudimentary stomach is often traceable whilst the larva is still within the egg. It measures about 1/500″ in length, including the peduncle, and 1/14000″ in breadth. The width of the narrow stalk does not exceed 1/9000″. The other two-stalked bodies appeared to have the character of lemnisci. They were occasionally well seen whilst the embryo was still within the egg. As regards the integument, it is easy to recognise two layers. In careful adjustments of the focus the inner wall of the transparent dermis presents a beaded appearance. These minute and regular markings do not undergo alteration during the contractions of the body of the larva.

A highly developed water-vascular system exists in these little animalcules. On many occasions I saw traces of this set of vessels, and in several instances I obtained a most satisfactory view of the entire series of branches. Anxious to receive confirmation of my discovery, I demonstrated the existence of these vessels to a skilled microscopist—the late Mr J. G. Pilcher, of H. M. Army. In the briefest terms it may be said that the water-vascular system of Bilharzia, in the larval condition, consists of two main stems, which pursue a tortuous passage from head to tail, and which, in the course of their windings, give off several anastomosing branches (fig. 19). As also obtains in the corresponding larvæ of Diplodiscus subclavatus, there is no excretory outlet visible at the tail.

Encouraged by the experiences and determinations of Pagenstecher, Filippi, Wagener, Leuckart, and others, I sought for the intermediate hosts amongst fresh-water mollusks and small crustacea. Failing of success in these, it occurred to me that the larvæ of Bilharzia might normally reside in fluviatile or even in marine fishes. This latter idea seems also to have struck Dr Aitken. In an appendix to his ‘Report to the Army Medical Department for 1868,’ dated from Netley, Nov., 1869, he gives a figure of a nurse-form, which he terms a cercaria, from the tail of a haddock—suggesting for Bilharzia some genetic relation. Dr Aitken also extends his views in reference to certain larval trematodes alleged to have been found in the so-called Delhi boils and Lahore sores. These parasitic forms have, however, been shown by Dr Joseph Fleming to be nothing more than altered hair-bulbs (‘Army Med. Reports,’ 1868–69).

In regard to the flukes from the haddock, I have satisfied myself that these immature trematodes from the nerves of the cod-tribe can have no genetic relation with Bilharzia; and I think it due to Dr Maddox to say that I accept his conclusion respecting them. In his paper (‘Micros. Trans.,’ vol. xv, 1867, p. 87) he offers strong proof that the so-called Distoma neuronaii Monroii of the haddock (Morrhua æglefinus) is the juvenile condition of Gasterostoma gracilescens of the angler (Lophius piscatorius).

I am sorry to have to state that all my experiments proved negative. I tried to induce the ciliated embryos to enter the bodies of a variety of animals, such as Gammari, Dipterous larvæ, Entomostraca, Lymnæi, Paludinæ, different species of Planorbis, and other mollusks; but neither in these, nor in Sticklebacks, Roach, Gudgeon, or Carp, did they seem inclined to take up their abode.

The very peculiar and formidable helminthiasis produced by this parasite has been thoroughly investigated by Griesinger and Bilharz, and it has been fully described in the standard works of Küchenmeister and Leuckart. My own case from Natal also supplied many interesting clinical facts which were published in my ‘Lectures on Helminthology,’ quoted below. The comparative prevalence of this disorder in Egypt is well established. Symptomatically, its principal feature consists in a general disturbance of the uropoietic functions. Diarrhœa and hæmaturia occur in advanced stages of the complaint, being also frequently associated with the so-called Egyptian chlorosis, colicky pains, anæmia, and great prostration of the vital powers. The true source of the disorder, however, is easily overlooked unless a careful microscopic examination be made of the urine and other evacuations. If blood be mixed with these, and there also be a large escape of mucus, a minute inspection of the excreta will scarcely fail to reveal the presence of the characteristic ova of Bilharzia. Besides the increase of mucus secretion, there may even be an escape of purulent matter, showing that the disorder has far advanced. The patient’s constitution eventually becomes undermined; pneumonia often sets in, and death finally ensues. On making post-mortem examinations the following pathological facts come to light. In cases where the disease has not advanced very far, minute patches of blood-extravasation present themselves at the mucous surface of the bladder, but in more strongly pronounced cases the patches are larger or even confluent. In some instances there are villous or fungus-like thickenings, ulceration and separation of portions of the mucous membrane, with varying degrees of coloration, according to the amount of the extravasation, which becomes converted into grey, rusty-brown, or black pigment deposits. A gritty or sandy deposit is often superimposed, consisting of ordinary lithic-acid grains mixed with eggs and egg-shells. Eggs are readily detected in the urine, these having escaped from the ruptured vesical vessels. The lining membranes of the ureters and renal cavities are also more or less affected; the kidneys being frequently enlarged and congested. It must, however, be borne in mind that in all these organs the true seat of the disorder is the blood, which forms the proper habitat of the Bilharzia; and this being the case, the worms as well as their escaped eggs may be found in any of the vessels supplying the diseased organs. In one instance, quoted by Leuckart, Griesinger found a number of empty eggs in the left ventricle of the heart, and from this circumstance it was supposed that they might be carried into various important organs, or even plug up the larger vessels. As before stated, however, the parasites are more particularly prevalent in the vessels of the bladder, mesentery, and portal system. The effects upon the intestinal mucous membrane are, in most respects, similar to those occurring in the urinary organs. Blood extravasations, with thickening, exudation, ulceration, and fungoid projections, appear in and upon the intestinal mucous and submucous tissues; these appearances, of course, being more or less strongly marked according to the degree of infection.

In regard to the treatment of the helminthiasis, I am precluded from entering into details here; nevertheless, I am glad to perceive that the principles which I long ago enunciated have received approval both at home and abroad. As stated in my ‘Lectures’ our object should be not to interfere with, but to promote nature’s curative efforts. If I read the pathological facts correctly, she seeks to bring about this result by erecting artificial barriers which serve to moderate the bleeding. In this way, under ordinary circumstances, the life of the bearer is sustained, or held in the balance until the parasites either perish or cease to be capable of causing active disease. Depend upon it, this is the principle which should guide physicians in their treatment of the Bilharzia disorder. If the adult parasite were merely attached to the lining membrane of the bladder, then powerful diuretics and medicated injections would probably prove serviceable; but since the entozoa reside in the blood we must be careful not to increase the patient’s troubles. In the case of intestinal worms the most powerful parasiticides may be prescribed without let or hindrance; but that drug must be a truly subtle worm-poison which, when taken into the system, shall kill the blood-flukes without exerting any injurious effects upon the parasite bearer.

When, in 1872, I published my lectures on helminthology, I remarked that it was not improbable that, ere long, many more cases of Bilharzia disease would be brought to light. What has been added in this respect is chiefly due to the researches of Sonsino, but a case of some interest has been recorded comparatively recently by Dr W. K. Hatch, stationed at Bombay. From the particulars furnished it seems evident that the victim, an English gentleman, contracted the disease by drinking water, either in Arabia or in Egypt, in which latter country, however, he had only sojourned fifteen days. From the patient’s statements it appears that, hæmaturia is frequent amongst the Arabs. Incidentally, Dr Hatch mentions that Dr Vandyke Carter had informed him that, so early as the year 1862, he (Dr Carter) had detected the embryos of Bilharzia in the urine of an African boy admitted to the Jamsetjee Jejeebhoy Hospital. The treatment employed by Dr Hatch was that recommended by Dr Harley in his well-known memoir. Having myself energetically opposed Dr Harley’s views on pathological grounds, I am not surprised to see it stated that Dr Harley’s method of treatment effected “no diminution in the number of the parasites.” As I said in my lectures (now out of print) it is evident that “nature” in view of moderating the hæmaturia—by the formation of plugs at the ulcerated points of the mucous surface—sets up the artificial barriers above referred to; therefore if you catheterise and employ medicated injections you do more harm than good. As to the administration of belladonna internally, in view of retarding development, or of destroying the parasite, no good can be expected from this source. I certainly obtained better results with buchu and bearberry (Arctostaphylos).

In the matter of sanitation it is quite evident, from the foregoing data, that the danger of infection cannot arise from the drinking of impure water, as ordinarily understood. The embryonal larvæ would be killed by an admixture of sewage. It is obvious that infection can only occur from swallowing free cercariæ or freshwater mollusks which contain the higher larval forms in their encysted or pupa condition. Slow running streams or stagnant pools with sedgy banks are eminently favorable to the existence and multiplication of intermediary bearers, and consequently their waters are dangerous if employed for drinking purposes.

Bibliography (No. 12).—Bilharz, in Siebold and Köll., ‘Zeitsch. für wissensch. Zool.,’ iv, 1851.—Idem, ‘Wiener medic. Wochenschrift,’ 1856.—Cobbold, T. S., “On some new forms of Entozoa (Bilharzia magna),” ‘Linn. Trans.,’ vol. xxii, p. 364, 1859.—Idem, “Synopsis of the Distomidæ,” in ‘Proceed. Linn. Soc.,’ vol. v, Zool. Div., p. 31, 1860.—Idem, “Remarks on Dr J. Harley’s Distoma capense,” in ‘Lancet,’ also in the ‘Veterinarian,’ and in ‘Intell. Observer’ for Feb. and March, 1864.—Idem, “Entozoa,” l. c., p. 197, 1864.—Idem, “On Blood Worms,” Lecture xx in ‘Worms,’ l. c., p. 145 et seq., 1872; Tommasi’s edit., Vermi, p. 141, 1873.—Idem, “On the Embryos of Bilharzia,” ‘Brit. Assoc. Rep.,’ 1864.—Idem, “On the Development of Bilharzia hæmatobia, together with Remarks on the Ova of another Urinary Parasite occurring in a case of Hæmaturia from Natal,” ‘Brit. Med. Journ.,’ July, 1872; repr. in the ‘Veterinarian,’ 1872.—Idem, ‘New Entozootic Malady, &c.’ (brochure), London, 1865.—Idem, “Helminthes,” in Gunther’s ‘Record of Zool. Literature,’ p. 617, 1865.—Idem, “Entozoa in relation to Public Health and the Sewage Question,” Rep. of the Proceed. of the Metrop. Assoc. of Officers of Health, in ‘Med. Times and Gazette,’ Jan., 1871, repr. in the ‘Veterinarian,’ p. 359, 1871.—Idem, “Verification of recent Hæmatozoal Discoveries in Australia and Egypt,” ‘Brit. Med. Journ.,’ June, 1876.—Idem, “On Sewage and Parasites, especially in relation to the Dispersion and Vitality of the Germs of Entozoa,” rep. in ‘Med. Times and Gaz.’ for Feb., and the ‘Veterinarian’ for May, 1871.—Davaine, C., l. c., ‘Synops,’ and p. 312, 1860.—Diesing, C. M., ‘Revis. d. Myzelmith,’ Vienna, 1858.—Griesinger, “Klin. und Anat. Beobachtungen über die Krankheiten von Egypten,” in ‘Arch. für physiol. Heilkunde,’ 1856.—Idem, ‘Gesammelte Abhandlungen,’ Berlin, 1872.—Idem, ‘Arch. d. Heilk.,’ 1866.—Harley, J., ‘On the Hæmaturia of the Cape of Good Hope, produced by a Distoma,’ rep. in ‘Lancet,’ and ‘Med. Times and Gaz.,’ Feb., 1864; also in Ranking’s ‘Abstract,’ p. 173, 1864, and fully in ‘Medico-Chirurg. Trans.,’ 1865.—Idem, “On the Endemic Hæmaturia of the South Eastern Coast of Africa,” ‘Med.-Chir. Trans.,’ vol. liv, 1871.—Idem, in Hooper’s ‘Vade Mecum,’ 1869.—Hatch, W. K., “Case of Bilharzia hæmatobia,” in ‘British Medical Journal,’ Dec. 14, 1878, p. 875.—Küchenmeister, F., ‘Parasiten,’ 1855; Eng. edit., p. 277, 1857.—Leuckart, R., l. c., s. 617, 1863.—Sonsino, P., “Richerche intorno alla Bilharzia hæmatobia in relazione colla Ematuria Endemica dell’ Egitto e nota intorno un Nematoideo trovato nel Sangue Umano,” ‘Estr. dal Rend., del. R. Accad.,’ 1874.—Idem, ‘Della Bilharzia hæmatobia e delle alterazione Anatomo-patologiche che induce nell’ Organismo Umano, loro importanza come Fattori della Morbilità e Mortalità in Egitto, con cenno sopra una Larva d’Insetto Parassita dell’ Uomo. Estratto dall’ Imparziale,’ Firenze, 1876.—Idem, ‘Sugli ematozoi come contributo alla Fauna Entozooca Egiziana,’ Cairo, 1877.—Idem, “La Bilharzia hæmatobia, et son rôle Pathologique en Egypte,” ‘Arch. Gén. de Médicine,’ for June, p. 650, 1876.—Idem, “Intorno ad un nuovo Parassita del bue (Bilharzia bovis),” ‘Estr. dal Rend. del. R. Accad. di Napoli,’ 1876.—Weinland, D. F., l. c., p. 67, 1858.

SECTION II.—Cestoda (Tapeworms).

Tænia mediocanellata, Küchenmeister.—This cestode is frequently spoken of as the unarmed or beef tapeworm. In general appearance it is very similar to the armed form. It is, however, a larger and broader animal, being at the same time rather stouter. It varies usually from fifteen to twenty-three feet in length, but specimens have been described as attaining thirty feet. It is called the unarmed tapeworm in consequence of the absence of any coronet of hooks on the head; and consequently, also, from there being no prominent rostellum or proboscis. The place of the last-named structure, however, is supplied by a small rudimentary disk, which I have seen protruded on pressure (fig. [20]). Usually this disk forms a more or less conspicuous cup-shaped circular depression, which has been compared to and described as a fifth sucker. That it is not, in any structural sense, comparable to the true suckers, I have had abundant opportunity of ascertaining; nevertheless, I do not doubt that it is to a slight extent capable of being used by the parasite as a supernumerary holdfast. The anchorage thus secured, however, is by no means equal to that obtained by the armed species. This explains the comparative difficulty we find in procuring a specimen of the armed tapeworm with the head attached.

Fig. 20.—Head of Tænia mediocanellata. Showing the calcareous corpuscles, suckers, rudimentary proboscis, and water vessels. Highly magnified. Original.

The establishment of this species as distinct from T. solium is due to Küchenmeister; but it is curious to observe how accurately this determination was foreshadowed by the shrewd naturalist and theologian, J. A. E. Goeze, who clearly indicated two forms of the common tapeworm, remarking (l. c., Bibl. No. 1, s. 278):—“Die erste ist die bekannte grosse, mit langen dicken und gemästeten Gliedern, die ich Tænia cucurbitina, grandis, saginata, nennen will.” The same author (s. 245) pointed out the resemblance subsisting between the tapeworm of the cat (T. crassicollis) and the vesicles (“Krystallblasen”) and their contained “erbsförmige Blasen” (Cysticercus fasciolaris) of the mouse. Thus the celebrated pastor of St Blasius, in Quedlinberg, almost contemporaneously with Pallas, early arrived at the conclusion that the hydatid-measle was a kind of tapeworm.

Fig. 21.—Free proglottides of Tænia medio­ca­nel­lata. After Leuckart.

Respecting the organisation of this worm I may observe that the mature joints have a more complicated uterine organ than obtains in Tænia solium, presenting nearly double the number of lateral branches. They are more closely packed, running outwardly in an almost parallel manner. The first sexually mature proglottis occurs at about the 450th joint, but whereas, in the pork tapeworm, only some 200 subsequent segments share this perfect character in the beef tapeworm, according to Leuckart, as many as 360 or even 400 mature joint may be present. The joints are very liable to form monstrosities; these abnormalities sometimes affecting the reproductive organs, which become doubled or even trebled. In the Hunterian collection there is a proglottid showing twenty-two sexual orifices. Dr Cullingworth, of Manchester, has described a specimen in which the joints are curiously tripartite.

As already hinted the true source of this parasite has been proved by experiment; the first successful worm-feeding having been accomplished by Leuckart. Mosler’s, and subsequently my own feeding experiments, immediately followed. Other successful experiments with this species have been conducted by Zurn, Probstmayer, St Cyr, Perroncito, Masse and Pourquier, and Zenker. As will be again mentioned below Dr Oliver, R.A., whilst stationed at Jullundur, successfully reared the adult tapeworm in a Mohammedan groom and in a Hindoo boy. It will also be seen that Prof. Perroncito reared the worm in a student in fifty-four days. In my own experiments on animals I was assisted by Professor Simonds. The feeding materials were tapeworms expelled from my own patients. We obtained the following interesting results:

Exp. 1.—A calf. First feeding, Dec. 21st, 1864. Marked symptoms. Slaughtered April 3rd, 1865. Result positive.

Exp. 2.—A calf. First feeding, April 13th, 1865. Second, third, and fourth feedings in May and June. No symptoms. Died on Sept. 3rd, 1865, after thirty-six hours’ illness with “cattle plague.” Result stated to have been negative as far as the muscles were concerned. Viscera not examined.

Exp. 3.—A Dutch heifer. First feeding, March 3rd, 1865. Three subsequent feedings. Symptoms only slight. Slaughtered April 4th, 1866. Result positive. Measles especially numerous in the diaphragm, but all had undergone calcareous degeneration.

Exp. 4.—A calf. Fed May 27th, 1872, with ripe proglottides. Marked symptoms set in on June 7th, which began to abate on the 12th, and had nearly disappeared by the 20th of the same month. The record of the post-mortem result has been lost; but the animal was infected.

Exp. 5.—A calf, which had been made the subject of a “glanders experiment.” First fed on Oct. 17th, 1872, and thrice in the following year, Jan. 1st and 11th, and March 8th. No symptoms having appeared the animal was kept for six or eight months after the last feeding. Seeming to be free from disease of any kind, it was sold as a sound heifer.

Exp. 6.—A young heifer calf, of six months. Fed Oct. 18th, 1873, with the mature proglottides of a large beef tapeworm. No symptoms. Slaughtered several months afterwards. Result stated to have been negative. Unfortunately I was not present at the autopsy.

Exp. 7.—A young heifer. First fed May 19th, 1874, with the joints of a tapeworm, and again on June 12th. No apparent ill effects resulted, but the animal died in October. At the post-mortem examination, made by Prof. Simonds, no parasites were observed. Subsequently I found calcareous specks in the liver which proved to be degenerated measles.

Exp. 8.—A calf. Fed on or about March 24th, 1875, with sexually mature joints. The calf was put to and remained with a foster mother until it died from disease of the larynx on the 15th of the following July. The animal was ill-treated by its foster parent, and at the post-mortem I observed a large intercostal cicatrix, evidently the result of injury. In this case I devoted several hours to the exploration of the muscles and viscera. Not a trace of the Cysticercus bovis could be found in the muscles or connective tissues, but the liver contained scores of perfectly developed measles, besides hundreds of others in various stages of calcareous degeneration. On comparing some of the latter with those I had obtained from the preceding experiment the pathological appearances were at once seen to be identical. It was easy to find and pick out the measles in their cysts from the naturally friable liver. I also detected four Cysticerci in the lungs, two of which had degenerated. Microscopic examination confirmed my interpretation of the naked-eye appearances.

Fig. 22.—Section of the heart of a calf infested by cestode larvæ. After Mosler.

Fragmentary as the above data are, they serve to show that we have hitherto been too hasty in concluding that beef and veal measles reside only in the voluntary and striated muscles of their hosts. The facts here recorded prove that the liver of a calf may be extensively invaded by cysticerci, and yet the animal will exhibit no sign of constitutional disturbance. The cestode tuberculosis may come and go without any diagnostic symptom, whilst a few months suffice for the natural death and decay of the parasite by calcareous degeneration. Thus it becomes extremely probable that many experiments hitherto regarded as negative in their results have really been positive; the pathological evidences having been either misinterpreted or altogether overlooked. Every pathologist is familiar with gritty particles in the various viscera of man and animals, but few are probably aware how constantly these are dead and degenerated Cysticerci. The gritty particle itself may be reduced to the merest point, no larger than the receptaculum capitis of the Cysticercus itself, and in course of time it will disappear entirely. Practically it is satisfactory to have experimental evidence of the fact that cattle, as well as other animals, however extensively measled they may have been, can become thoroughly cleansed of the disorder by nature herself. It is only necessary that the diseased animals be separated from infectious influences.

Although the beef measle has never yet been found in man, I have for convenience sake introduced the facts of larval parasitism in this place. The sanitary bearings of this subject are far too important to be dismissed in a summary manner. I have shown that the prevalence or rarity of the beef tapeworm in man is strictly dependent upon the habits of the people; this same cause operating to produce healthy or diseased meat-food, according to the degree of civilisation. In this connection the oft-quoted statements of Kaschin respecting the prevalence of tapeworms among the Burätes, and the well-known frequency of this entozoon in Abyssinia, need only be alluded to.

When discussing the food question in my ‘Manual,’ I freely availed myself of facts privately communicated by Dr Joseph Fleming, and I especially referred to the published labours of Lewis, Hewlett, Veale, and other observers stationed in India. Beef measles are extremely common in the cattle of the north-west provinces of India, so much so that severe restrictions have been imposed upon the consumption of ration beef. The presence of a few measles in the flesh of cattle has been deemed a sufficient excuse for condemning and burying entire carcases. The measle is easily distinguished from that of mutton and pork by the fact that its head is not furnished with hooks, whilst in the place of a rostellum there is a small, centrally placed, retractile disk, which assumes the appearance of a supplementary sucker as in the adult worm. The four true suckers are also comparatively large. The measle usually varies in size from the fourth to the half of an inch in length, but my cabinet contains a specimen nearly an inch long. This was contributed by Dr J. Fleming, who mentions having seen a measle which, when unrolled, measured nearly an inch and a half in length. Although thousands of these bladder worms must exist in the cattle of England, up to the present time not a single instance has been recorded of the occurrence of these cystic parasites in the United Kingdom, except in our experimental animals. Notwithstanding my inquiries, I have not yet found a butcher, flesher, meat-inspector, or veterinarian, who has encountered this parasite in any animal slaughtered for the market. Several butchers have denied their occurrence in meat sold by themselves. Even so late as June, 1874, the presence of measles in the flesh of cattle was denied before an assembly of French savans; yet for many years past I have constantly exhibited measly beef and veal in the lecture room of the Royal Veterinary College. (See the discussion of the Société de Thérapeutique, recorded in the ‘Bullétin Gén. de Thér.’ for June 30th, 1874, and also the ‘Jour. de Thér.,’ No. 14, for July, p. 556, where, however, special remarks on this head have been omitted; see also the ‘Lond. Med. Record’ for July 29th, 1874, p. 472, and the ‘Lancet’ for Dec., 1874, p. 794.) Quite in contrast with the statements referred to are those of recent Italian observers.

Some few years back Professor G. Pellizzari communicated to the Medico-Physical Academy, at Florence, the results of a series of experiments conducted by himself, with the assistance of Dr Tommasi, in regard to the temperature necessary for the destruction of cysticerci in measled meat. An account of these experiments is published in Tommasi’s edition of my ‘Manual.’ The researches were made in relation to certain sanitary measures effected by the Municipal Commission of Florence, the express object of these measures being to prevent the injurious distribution of measly meat, especially that of swine. Signor Bosi, the superintendent of the public slaughterhouses, granted every facility in his power. In a previously published memoir by Professor E. Perroncito it was stated that measly meat (panicatura degli animali) required a higher temperature than that of boiling point for the destruction of the bladder worms in question. In this opinion Signor Bosi shared. According to the original memoir of Perroncito we are told that “about twenty specimens of Cysticerci were collected by the author, and placed in boiling water. After twenty minutes’ boiling, not one of the parasites appeared to suffer. The head continued to be drawn into the body, and when the Cysticerci had their heads drawn out one by one they still appeared to possess all the elasticity of living bladder worms, displaying those movements of extension which are proper to parasites not yet dead. The hooks were observed regularly disposed on the proboscis, where they formed a double crown, the suckers remaining intact.” Perroncito remarked, however, that the Cysticerci showed a coloring tendency towards brown, and he added that “with the aid of two needles it became easy to lacerate the body of the Cysticercus, which appeared to be swollen, and possessed of diminished cohesion of its parts.” It was evident to all eyes, observed Professor Pellizzari, that these statements involved clear contradictions. Yet again, at page 28 of the memoir, Professor Perroncito wrote:—“During the past winter I introduced some little slices (fettuccie) of muscle-flesh (8 to 10 millimètres in thickness), infested with Cysticerci into a vessel (cassolina) containing fat at the temperature of 190 to 200° Cent. (374 to 400° Fahr.). At the expiration of ten or fifteen minutes the slices of meat were fried, and the Cysticerci lying at the surface had acquired a light brownish colour, as if they were roasted. By breaking up the slices one could still see the small reddish muscular bundles, whilst the Cysticerci in the middle remained entire and well preserved. Their heads displayed the hooks and suckers regularly distributed.” It is certainly singular, as Pellizzari observes, that these Cysticerci, having been thoroughly fried and roasted, should still remain alive and in their normal state; but the ultimate conclusion at which Perroncito arrived was still more startling, and one which, if it were true, would not fail to create a considerable stir among our officers of health. On reviewing the whole matter Perroncito says:—“It appears to me that the melted fat alone of hogs (maiali grandinosi) should be utilised, and I am pleased to reckon the illustrious Gerlach and all other distinguished practitioners to be of the same opinion. Permit me, therefore, being well satisfied also with the results of many other experiments, once more to advance the conclusion that, if it is not certain that the Cysticerci die at from 80 to 100° Centigrade (176 to 212° Fahr.), we are quite sure that they dry up and become completely mummified at 125, 130, and 150° Cent. (257, 268, and 302° Fahr.), temperatures which we could easily produce by means of a properly constructed apparatus.”

After remarking upon the serious nature of the conclusion which Perroncito sought to establish, Professor Pellizzari makes further use of quotations which bear upon the question as to whether the quality of the vessels in which the fat of diseased hogs is melted down may not largely affect the degree of high temperature sought to be obtained (in view of a perfect destruction of the Cysticerci). Perroncito repeatedly witnessed the operations of pork-butchers; and when portions of meat were introduced, with water, into the cauldrons, he always saw that the temperature “was maintained between 97° and 98° Centigrade.” However, this part of the question may be dismissed in a very few words, since Perroncito himself finally allows that “the different composition of the vessels cannot elevate the temperature of the fat by many degrees.”

With the praiseworthy intention of either verifying or refuting these conclusions, Pellizzari, with the approval of Bosi and with the assistance of Tommasi, instituted a fresh series of experiments at a private laboratory. The details of these experiments are exceedingly interesting; but as their record occupies several pages of Tommasi’s appendix already referred to, I must content myself with a general statement of the results obtained. Professor Pellizzari found that Cysticerci, so far from requiring a temperature of upwards of 100° Centigrade for their destruction, die at a temperature of 60° Centigrade (140° Fahr.). He had, it appears, previously taken the initiative in recommending certain measures to the Florentine municipality, in view of protecting the public health, and he had now the satisfaction of more than confirming the wisdom of these sanitary precautions. In excessively measled animals the fat is removed and boiled in suitable cauldrons, and has potash mixed with it to render it useful for industrial purposes. By the various measures adopted the entire animal is utilised, and with proper precaution there seems little chance for the measles to arrive at the tænioid or sexually mature condition.

In the next part of his communication Pellizzari touches upon the question of measles in beef, referring especially to the experimental labours of Leuckart and myself. Finding additional support from our views Pellizzari declared the propositions of Dr Perroncito as of no value whatever. “But how is it,” he adds, “that notwithstanding that so low a temperature suffices to kill these cysticerci, yet cases of Tænia are continually occurring?” The answer to this question will appear in the sequel; but meanwhile it will be as well to refer to the recent brochure by Dr Giacomini. This author appears to have had no opportunity of perusing Pellizzari’s communication already cited, and consequently it is not surprising that he should, in common with others, have accepted the original conclusions of Perroncito. Dr Giacomini clearly perceives that, whatever precautions of a hygienic character are suitable for the prevention of disease arising out of the consumption of measly pork, the same, or at all events similar, measures ought to be adopted with the view of checking tapeworm affections arising from the ingestion of other kinds of meat, especially veal and beef. Like Pellizzari, he is satisfied as to the human origin of the small bladder worms found in cattle, and establishes this position not only from the oft-quoted experiments of Leuckart and Mosler, but also from those conducted by myself and Simonds in England, and by Professor F. Saint-Cyr in France. From a careful review and consideration of all the facts of the case, he recommended a more complete supervision over the flesh of oxen before it is employed commercially, and greater precaution when employing veal as food, by causing it to be subjected to a high temperature, in order that the parasites may be killed before it is ingested. It is evident that Giacomini thinks that a temperature exceeding that of boiling-point is necessary for the destruction of the beef and veal measles, since he immediately adds, “Though experiments have not been made with the object of ascertaining the amount of resistance of heat which the unarmed cysticercus can bear, yet, judging by those conducted by Professor Perroncito on the measle of the hog, we are in a position to say that a temperature of 135° Cent. (275° Fahr.) is necessary for the destruction of an isolated Cysticercus, whilst the heat should be raised from 150° to 200° Cent. (302° to 392° Fahr.) for ten or fifteen minutes, in order to ensure the complete destruction of the Cysticerci encapsuled in the interior of a piece of meat.” I have abridged this portion of Giacomini’s text, because his statements are pretty much the same as those already quoted from Perroncito (as cited by Tommasi). But, in the next place, Dr Giacomini is in error when he states that experiments had not been performed on the Cysticerci of the ox. So far from this being the case, similar experiments had long previously been conducted by Dr Lewis in India; and these researches had quite as much to do with the measles or Cysticerci of beef as they had with those of the hog, if not more. Naturally but few foreign investigators can have had access to the work in which Lewis’s experiments were originally recorded, and to which, therefore, I must call their attention. Thus, Dr Tommasi has fallen into the error of supposing that the investigations of Lewis were made in England. It is of very little moment where the experiments were carried on, but Tommasi’s statement (appendix, loc. cit., p. 161), wherein he says that Pellizzari’s experiments, in which he himself took part (ai quali io stesso ho assistito), are even more complete than those made in England by Dr Lewis, and in Germany by Dr Küchenmeister, cannot be allowed to pass unchallenged. If Tommasi had enjoyed the opportunity of consulting Lewis’s original memoir, he would not have underestimated our countryman’s labors. The memoir by Lewis is singularly complete, and well-nigh exhausts all the facts that can have any interest in relation to the question of public health. Towards the close of his essay he expressly states, as the result of investigation—“(1) That exposure to a temperature of 120° Fahr. for five minutes will not destroy life in Cysticerci, but that they may continue to manifest indications of life for at least two or three days after such exposure; (2) that exposure to a temperature of 125° Fahr. for five minutes does not kill them; but (3) after being subjected to a temperature of 130° Fahr. for five minutes, they may be considered to have perished. After exposure to this and higher temperatures, in no instance have I been able (he adds) to satisfy myself that the slightest movements took place in their substance when examined even under a high power. At least, it may be confidently asserted that, after exposure for five minutes to a temperature of 135° to 140° Fahr., life in these parasites may be considered as absolutely extinct” (p. 139). Thus the statements of Lewis and Pellizzari were in perfect accord; and seeing that their conclusions were alike the result of very careful and independent inquiry, it seemed as if the question at issue was finally solved. These investigations made it perfectly clear that Cysticerci of all kinds, whether found in veal, beef, or pork, could not retain their vitality when exposed to a temperature of 60° Centigrade, or, in other words, 140° Fahr.

The rather severe strictures made on Perroncito’s earlier experiments induced the Turin professor to go over the subject more carefully, when he obtained excellent results. He finally ascertained that Cysticerci perished at a temperature below 50° C. (122° Fahr.). In May, 1877, Dr Perroncito furnished me with an account of his researches. With the exception of a few verbal alterations, for which I am responsible, Perroncito wrote as follows:

“In order to resolve the highly important question of the tenacity of life of the Helminths and corresponding larval forms, I made since 1871 a very long series of experiments on the Cysticercus cellulosæ, which were published almost at the same time with others of the same kind, made by Dr Lewis in Calcutta. Towards the end of 1874 Mr Pellizzari, of Florence, disputed the results of the investigations which I had made known two years before, i.e. in 1872, and agreed with Dr Lewis, who had stated already that the Cysticercus exposed to a temperature of 55° C. can be held for dead after five minutes, and also with Dr Cobbold, who thought the temperature of 60° C. quite enough to kill it. But the characters he (Mr Pellizzari) relied upon, needing the exactness and precision required to enlighten and persuade in the most important scientific questions, gave rise to a mistrust in the most scrupulous amongst the men devoted to biological pursuits and to several hygienic measures on the part of the sanitary inspectors with regard to infected pork. Therefore, my conclusions, argued from the experiments made in 1871–72, were still those followed by the most important Italian cities, and approved in principle by the superior Board of Health in 1873. I expressed doubt then about the Cysticercus dying at a temperature lower than 100° C., and some person misconstrued these doubts, saying that I had contradicted myself in my work. However, as I could not assert they died at 80°–100° C., I only noticed the alteration of color and cohesion which happened in the Cysticercus exposed to various degrees of temperature, to the end that I might contribute usefully to the solution of the difficult question, and concluded that ‘if we could not be sure of the Cysticercus dying at 80°–100° C., it was certain at all events that they perished at 125° or 130° C.’ Not wishing to prejudice the question, I never said that they did not die at 80°–100° C., but simply stated that at this temperature we could not be certain of their death.

“Now, after a large number of experiments, I have been able to ascertain with exactness the lowest degree of temperature required to kill infallibly the Cysticercus and other parasites of animals. The means I made use of for this kind of investigation were Mr Schulze’s heating table, the neutral tincture of carmine, the tincture of hæmatoxylon, and breeding experiments.

“My method is founded essentially—

“(a) On the fact that the Cysticercus when it is fresh and is stretched and conveniently prepared in pure water, or in chloride of soda very much diluted, and afterwards brought gradually from the temperature of the ambient air to that of the body of higher animals and to degrees of heat still more elevated, until life is extinct, keeps moving to and fro with more or less energy throughout its body, using especially its suckers and proboscis.

“(b) On the greater imbibing power of the dead tissue generally, which is undoubtedly far more apparent in insects and plathelminths.

“(c) On the experiments made to ascertain the value of the two above-stated facts.

“If, after having prepared a Cysticercus, newly extracted from a pig in the way we have pointed out, we examine it with a microscope on M. Schulze’s heating table, we find that usually it begins to move after 30° or 35° C., and each moment with greater activity, especially after 38°, 40°, 42°, 44°, 45° C. The temperature being raised progressively, we see that the Cysticercus cellulosæ puts a stop to its movements occasionally at 45–46° C., seldom at 47° C., more frequently at 48° C., sometimes at 49° C.; and, in fifty and more experiments, only one Cysticercus was able to live on beyond 49° C., standing still at 50° C.

“As soon as it stands still the parasite is dead. In fact, if we lower again the temperature gradually to that of the ambient air, and if afterwards we raise it a second time, we pass through all the intermediate temperatures without the Cysticercus showing the least signs of life.

“But a more convincing proof of the death of the parasite is got from the greater imbibing power of the tissue when life is extinct, the same over the whole body of the plathelminths, and their larval forms. If we dip the Cysticercus alive with its head stretched in the neutral tincture of carmine or hæmatoxylon we can leave it there even two, four, eight, ten, or twelve hours and more, without the head coloring or a real imbibition taking place; this begins only after the Cysticercus is dead, so that if the Cysticercus is brought first to a temperature hot enough to kill it (with M. Schulze’s tables to one of 48°, 49°, 50° C.) and dipped afterwards in the above-mentioned tinctures, it colors intensely in less than 45°, beginning from the head, and onwards to the extremity of the cyst of the tail. The head colors more intensely and rapidly than the neck, as it is covered with very numerous calcareous corpuscles, which are not met with so frequently in the remaining part of the body.

“Cysticercus cellulosæ of the pig, and that of the Tænia mediocanellata of the calf, brought gradually to a final temperature, the first of 50° C., and the second of 44°, 45°, and 47° C., and then swallowed alone, or with a piece of butter or crumb of bread, never produced the Tænia in the valiant students who voluntarily undertook to make the experiment of swallowing them.

“My investigations were extended to other kinds and forms of Helminths, and the results were always the same, so that, abiding by the same principles, I was able to ascertain that—

“1st. The Cysticercus cellulosæ of the pig dies sometimes at 45° C., more frequently at 47° C., ordinarily at 48° C., very seldom reaches alive 49° C., and is quite an exception when it resists for a few moments the temperature of 50° C., so that we can say that the Cysticercus brought gradually up to this temperature most assuredly dies if it is kept there longer than one minute.

“2nd. A Cysticercus cellulosæ, extracted by Professor Raymond from the conjunctiva of a child’s eye, died between 45° and 46° C.

“3rd. The Cysticercus of the Tænia mediocanellata dies sometimes at 44° C., very often at 45° C., and does not resist a temperature superior to 46° C.

“4th. The Cysticercus pisiformis of the rabbit, like the cellulosæ, dies sometimes at 45° and 46° C., but generally stands still and perishes at 47° and 48° C.

“5th. A Cysticercus tenuicollis died at 49° C.

“6th. The scolici of the Cœnurus cerebralis of a sheep died at 42° C.

“7th. The scolices of the cysts of Echinococcus polymorphus die generally between 47° and 48° C., and in no case amongst those I have experimented on did it reach 50° C. alive.

“8th. The Tænia cucumerina died, one at 43° C., and a second parasite at 45° C.

“9th. A few individuals of Tænia serrata of the dog died at 50° C.

“10th. Two individuals of Tænia perfoliata of the horse died, the first at 45° C., the second at 50° C.

“11th. The embryos of the Filaria microstoma of the horse began to stand still at 46–47°, and all died at 48° C.

“12th. The embryos of the Filaria megastoma of the horse’s stomach died at 47° C.

“13th. The Trichina spiralis, both free and in a cyst, in several experiments always died at 48° C.

“14th. The embryos of the Strongylus filaria of the sheep stood still at 50° C.

“15th. Probstmayer’s viviparous oxyurids, the infusoria of the colon and cæcum of the solipeds, and the psorosperms of the liver of the rabbit did not stir at all.

“Each experiment lasted about ten minutes, and the temperature rose from 8–10° C. to 45–46° C. in six to eight minutes; and from 46° to 50° in one minute. These experiments have a great value, both scientific and practical, as they show, on one side, which is the lowest intensity of heat sufficient to kill always the Cysticercus, the Trichina, and other parasites, reducing thus by far the tenacity of life generally attributed to a large number of Helminths and corresponding larval forms. They assure us, moreover, of the harmlessness of the flesh infected by the above-mentioned parasites, when it is cooked in such a manner as to reach the temperature of 50° C. over all points of the pieces, even though it be kept at such a degree of heat not longer than five minutes.

“In a piece of leg of pork the Cysticerci were found alive in all places not yet putrefied twenty-nine days after the animal had been slaughtered. On the other hand, in the dry muscles of a calf the Cysticerci of the Tænia mediocanellata were all found dead fourteen days after the slaughtering of the animal. I have ascertained that putrefaction of the flesh is fatal for the two larval forms of these different kinds of helminths.”

In a subsequent communication received from Professor Perroncito towards the close of the year 1877 he writes:

“At the last meeting, held on April 23rd, I made a statement to the Medical and Surgical Society of Turin, of the results of other experiments tried by heating at M. Schulze’s table and by the imbibitions with the neutral tincture of carmine, through which I came to the conclusion that the Cysticerci of the Tænia mediocanellata die sometimes at 44° C., now and then at 45° C., and always at 46° C. I therefore concluded that they could in no case survive at 47° C. and 48° C. when they were maintained at this temperature at least five minutes. But to the end of more fully corroborating the facts I had thus communicated, I, contemporaneously with these, made some breeding experiments with the same Cysticerci on bold and courageous students who generously offered themselves for the benefit of science.

“Consequently I am now enabled to state that neither Mr Gemelli nor Dr Ragni contracted the Tænia, though each of them had eaten a Cysticercus of the Tænia mediocanellata previously, and respectively subjected to a temperature of 45° C. and 47° C. The larvæ were properly prepared and submitted to gradual heating on the above-mentioned table, and swallowed when they no longer gave signs of life. In like manner no generation of the Tænia took place in the body of Mr Martini, who ate the Cysticercus brought to a temperature of 44° C. It was maintained at this degree of heat during a period of about three minutes, and swallowed whilst a very slight movement was still visible in a portion of its neck.

“In another student, on the contrary, who ate a living Cysticercus of the Tænia mediocanellata, the tapeworm reached its maturation in fifty-four days and eliminated the two first proglottides. It threw off two more on the fifty-eighth day, and thirty on the sixtieth. Sixty-seven days after swallowing the Cysticercus this courageous young man, having, like his three companions, taken some kousso and castor oil, emitted the strobila. It was furnished with 866 rings, but destitute of the neck and head. Its measurement afforded a total length of 4·274 mètres.

“Adding now to the 866 proglottides the thirty-four already eliminated, 900 would be the number of the segments; and reckoning the length of each of the latter to be fourteen millimètres, we should have had the strobila (deprived of the head and neck) reaching a length of 4·75 mètres. Further, calculating the head and neck to be eight millimètres long, a total length of 4·83 mètres would be the result.

“From all these facts we may conclude that the Tænia has, in our instance, reached an approximative length of seventy-two millimètres a day, affording a daily production of 13·43 proglottides.”

In relation to requirements of state medicine I have thought Perroncito’s researches sufficiently valuable to be quoted at some length; but their chief interest culminates in the worm- feeding experiments. Excellent in all respects as was the conduct of the medical students who, with Professor Perroncito’s approval, swallowed living specimens of the Cysticercus bovis, the intentional ingestion of beef measles is by no means a novelty. Eight or ten years back Dr Oliver (after explaining to one of the selected victims the possible consequences of the experiment) induced a Mahommedan syce or groom and a Hindoo boy to swallow perfectly fresh and living beef measles. In this way Dr Oliver successfully reared the Tænia mediocanellata in India, and he was thus enabled to fix the amount of time necessary for the full growth of the strobila. Many other persons have displayed an equal amount of zeal in the cause of helminthology, by partaking of the larvæ or germs of other parasites. Thus, at the risk of repetition, I may state that Möller many years ago swallowed the slender-necked hydatid (Cysticercus tenuicollis) in the hope of infesting himself with Tænia marginata. Several persons have defiantly swallowed trichinised flesh. Professor Leuckart and some of his pupils also courageously swallowed the eggs of Oxyurides, and they had the infinite satisfaction of noticing the young worms in their fæcal discharges some fifteen days afterwards. Dr Crisp ate part of the cooked flesh of an animal that had died of cattle plague, and I myself partook of moderately cooked meat which I knew to be swarming with psorosperms. These obscure organisms were by some persons considered to be either a cause or product of the rinderpest. They will be noticed in my account of the Protozoal parasites.

For the purpose of advancing science and the welfare of the people, there are scores of persons always to be found ready to make personal sacrifices of the kind undertaken by Drs Ragni, Martini, and Gemelli. Unfortunately for English science there are not wanting people in this country who are prepared to threaten with fines and imprisonment any savant who may think it desirable to perform a similar set of feeding experiments on animals. Invaluable for good as our experimental investigations have already been, it would seem as if it were the deliberate aim of these sentimental obstructives to put a stop to the acquisition of all useful knowledge in the future.

In reference to the rate of growth of tapeworms, Professor Perroncito’s determinations are useful, inasmuch as they verify certain ascertained facts with precision and confirm the general conclusion that had been drawn by practical helminthologists from various sources of information. In regard to the number of proglottides proper to a sexually mature tapeworm, the circumstance that Perroncito’s calculation was made without the head and a portion of the neck of the worm being present shows that it cannot be relied on absolutely; nevertheless, as far as it goes, it tends to confirm what Leuckart had long previously stated. I have possessed myself of upwards of thirty perfect beef tapeworms expelled from my patients, and in some of the specimens it was noticed that the segmentation-rings in the region of the neck were far more crowded together than they were in others. I also possess a perfect Tænia mediocanellata, removed post mortem. Though the rate of growth may be the same from day to day, yet experience has shown that the number of proglottides actually cast off varies exceedingly. Küchenmeister’s estimate of the average number agrees in the main with what we have ourselves observed (five to twenty daily); and here again Perroncito’s investigations serve to verify the general correctness of our previous determinations.

To return to Pellizzari’s researches, one of the most important questions is that which relates to the prevalence of tapeworm. In this connection he first brings forward some very interesting and instructive data that had been previously communicated to the Medico-Physical Academy of Florence by Professor Marchi. On the occasion referred to Marchi had stated that, out of thirty-five Tæniæ which he had examined, only one belonged to the species known as Tænia solium; all the other thirty-four being of the unarmed type, or Tænia mediocanellata. Reflecting on this striking fact, and also on the circumstance that he had in vain begged his colleagues to send him specimens of Tænia solium, Marchi seems to have missed the very palpable explanation of this otherwise strange phenomenon. “How does it happen,” exclaimed Marchi, “that, notwithstanding the occurrence of 13,000 kilogrammes of the flesh of measled hogs in the public butcheries, I have seen but one specimen of Tænia solium, whilst thirty-four cannot have originated from the pig?” “The wherefore is obvious enough,” replies Pellizzari, “because our hygienic regulations demand that the flesh of the hogs be raised to a temperature of 60° Cent. (140° Fahr.);” and he then himself immediately proceeds to ask another question, namely, as to how it happens that the Tænia solium is so frequently seen in other places. To his own question Pellizzari responds by remarking—(1) that there are not so many precautions (of a sanitary kind) taken in other places; and (2) that the people elsewhere consume more slightly salted or uncooked meat, as sausages and so forth (come salame giovane, salciccia e via dicendo). Pellizzari, having explained that Marchi’s thirty-four tapeworms must all have arisen from the consumption of the Cysticercus of the ox, then goes on to speak of the prevalence of tapeworm in Florence, even in little children. This last-named feature, he says, is due to the circumstance that raw meat is frequently employed as a restorative (come cura ricostituente). “Thirty years ago,” remarks Professor Pellizzari, “it was just as difficult to find a single Tænia mediocanellata as it is now easy to find a great number of these worms; and all because it is nowadays customary to eat the flesh of the ox either insufficiently cooked or raw. This absolute inversion of the facts of the case affords proof of the correctness of the position sustained by me, to the effect that the cooking of meat up to the degree of temperature necessary for ebullition ensures the destruction of the Cysticerci.” Notwithstanding this statement of his own, Pellizzari thinks that the interference of inspectors may be pushed too far, and thus serve to bring about the very disasters which it should be their supreme object to prevent. Thus, he argues against the suggestions of those who would entirely prevent the sale of measly meat, and who would only permit, as obtains in the province of Modena, the melting down of the fat of hogs. Very strict measures of this sort would, as he says, constitute a radical means of entirely stamping out Tænia, but he also very judiciously reminds the sanitarian (igienista) that “such a step would be a serious thing for the tradesman, bringing injury not only to the municipal administration, but also proving an encouragement to smuggling. In this way the public health would sustain worse injury by the inducement held out to the owners of infected animals to slaughter them in secret butcheries, thus little by little withdrawing the meat from the superintendence of the public officials. By the adoption of fraudulent measures there would be a daily consumption of diseased meat; and thus also, while the public administration would suffer loss, the public health, on the other hand, would gain nothing.” In effect Pellizzari says, if we advise the employment of more severe and radical measures than those already in vogue in Florence, we should overburden the tradesman, almost compel him to defraud the exchequer by smuggling, and greatly injure the public health.

The facts and explanations advanced by Italian writers regarding the causes of the endemic prevalence of tapeworm, are in perfect harmony with those previously obtained from other sources. Respecting these causes there is much that is both new and interesting. The eighth annual report of the sanitary commissioner of the Government of India had already made us acquainted with the fact that during the year 1869, out of 13,818 head of cattle slaughtered in the stations of the Upper Punjab, 768 beasts were found to be infected with measle-cysts. This, as I have remarked (Tommasi’s edit., p. 54), “affords a rate of 5·55 per cent., being a considerable diminution of the proportion observed in 1868, when the percentage gave a total of 6·12. The reduction was, without doubt, due to the vigilance and enlightenment of the army meat inspectors. The prevalence, however, of tapeworm does not bear relation to the number of animals infested with Cysticerci so much as to the actual number of Cysticerci developed in infected animals. I have frequently pointed out the inadvisability of condemning and burying the carcases of measly oxen, whether there be few or many Cysticerci present, and I have stated, on trustworthy evidence, that even the presence of a few Cysticerci is deemed by some inspectors a sufficient reason for rejecting the entire animal. Such a waste should never be allowed. In regard to the numbers of ox-measles present in particular instances, I have elsewhere adduced some remarkable facts communicated to me by Dr Joseph Fleming, of the Indian Army Medical Staff. None of my experimental animals, though fed with scores of ripe proglottides, yielded such an abundance of Cysticerci as Dr Fleming encountered in Punjab cattle. In one pound weight of the psoas muscles Fleming counted no less than 300 Cysticerci.” From this it follows that the flesh of a largely infested animal is capable, under the circumstances of ration distribution and imperfect cooking, of originating numerous tapeworms.

Not many years back the leading medical journal of this country challenged me to produce evidence as to the injuriousness of beef and mutton from Cysticerci. The writer stated in his article that I had “failed to produce a single specimen of beef or mutton measles” which had not resulted from experiments conducted “at the Royal Veterinary College;” and he said, further, “that butchers, fleshers, and veterinarians were practically right in refusing to adopt the opinion of Dr Cobbold, that measled beef or mutton is produced to any great extent” independently. How palpably I endured a species of unjust reproach for being somewhat in advance of the knowledge current at the time may be gathered from the voluminous evidence which has since cropped up from various parts of the world. It was, indeed, mainly through experiments conducted at the Royal Veterinary College, and reported in the ‘Lancet,’ that professional men in India first became acquainted with the possibility of finding Cysticerci in beef.

The statements of Dr Joseph Fleming, who was one of the foremost in discovering cystic disease in cattle, have since received abundant confirmation. The Indian Government Reports given in the February issue of the ‘Madras Monthly Journal of Medical Science’ for 1873 are especially instructive. Referring to the prevalence of Cysticercus in the ration beef at Jullundur, in the Punjab, the Inspector General (India Medical Department) reports as follows:

“Cysticercus was first noticed here in the beef tendered at the Royal Artillery ration stand in May, 1868. For some two years previous to this date condemnations of cyst-infected meat had been frequent at Peshawur, Rawul Pindee, Meean Meer and several other stations in the upper part of the Punjab, and here I had often detected the parasite in meat exposed for sale in the bazaars, but no trace of it had been observed in the Commissariat beef, either by myself or any other medical officer who had preceded me.

“From May, 1868, to November, 1869, ‘cyst’ was more or less frequently found both at the Artillery and 92nd Highlanders’ ration stands; but since the latter date it has almost entirely disappeared.

“The following table shows the quantity of meat destroyed on this account during 1868 and 1869:

“The whole of this meat was otherwise well fed and of excellent quality. The waste of so much good food led me to make inquiries; 1st, as to the sources from which the cattle obtained the Tænia ova, and the best means for preventing their infection; and 2ndly, as to whether or not any evil results followed the consumption of this meat when properly cooked.

“From information obtained from the Commissariat Officer I found—1st. That the infected cattle had been purchased by native dealers from various parts of the district, not from any particular locality. 2ndly. That when brought in they were lean, and on an average required from two to three months’ feeding at the Commissariat cattle yards before they were fit for the shambles. 3rdly. That their food consisted of the grass they could pick up on the grazing grounds of cantonments, supplemented by such an allowance of grain and bhoosâ as their condition required.

“They were supposed to be watered at a trough with water drawn from a well, but on closely inquiring as to this, it transpired that they very frequently were taken to a large dirty tank near the yard for their water. The question which occurred to me was, were the cattle infected before their purchase by the Commissariat, or was there anything in their feeding to account for it after purchase? I am inclined to the latter opinion for several reasons, thus:—In the large number of the diseased cattle, the Cysticerci were of remarkably small size; many of them having no capsules, except such as were formed by the surrounding structures, and not being more than 1/8 to 1/4 of an inch in diameter. Although the dry food given to the cattle was doubtless good, still much of the water they got during 1868 was probably filthy. The tank previously referred to was situated close to the huts of the camel drivers. These men are all Mussulmans from Cabul, Peshawur, or thereabouts, and many of them are infected with Tænia mediocanellata. Human filth was often to be seen on the banks of the tank, and microscopic examination of mud and stagnant water taken from the margin exhibited Tænia ova.

“The conditions above shown must have been eminently favorable to keeping up a constant supply of ova, and the fact that Cysticercus entirely disappeared from amongst the cattle a few months after means had been taken to secure them a good supply of well water, seems to confirm the view that this tank must have been the source of a large amount of, if not all, the infection.

“It has been suggested that Cysticercus can be detected before the animal is killed by an examination of the tongue. In exceptionably severe instances this is probably correct, but then it would be equally observable in some other parts of the body. Major Biggs, Commissariat Officer here, tells me of an animal he saw at Rawul Pindee, in which immense clusters of cysts could be felt at the root of the tongue and under the skin in several parts. After examining a very large number of tongues of ‘cysted’ animals, my experience is that it is found in the soft muscles and cellular tissues at the root of the tongue, perhaps more frequently than anywhere else; but I have never seen a case in which there was a chance of detecting it before death.

“The most common situations in which it has occurred in the ration meat have been the gluteal, psoas, and lumbar regions. In many instances only from one to ten cysts have been found on cutting the carcase into small pieces, and I have no doubt that it often passed without detection.

“During 1868 and 1869 I from time to time obtained pieces of beef badly infected with Cysticercus, and made some experiments as to the results of its consumption under different conditions.

“After explaining to them the possible consequences of eating it a buttock of beef studded with Cysticercus was given to three natives of low caste. They all declared that they were free from Tænia, or, to use their own term, “Kadhu dana.” The meat they cooked in their own way. These men were under my observation for some six months. Two of them had no symptom of Tænia, but the third, who was a low-class Mahommedan syce, and had probably eaten the meat in a very raw state, developed a Tænia mediocanellata in about three months.

“My own sweeper ate this cyst-infected beef regularly two or three times a week for some months. He cooked it well generally as an ordinary stew, and has never shown a sign of having tapeworm.

“Into the food of a boy of low Hindoo caste, but who had never eaten beef, two scolices of Cysticercus were surreptitiously introduced, the result being that, between three or four months afterwards, he applied for some tapeworm medicine.”

[The two successful experiments here reported are evidently the same as those that I have referred to (p. [72]) as having been performed by Dr Oliver, of the Royal Artillery, stationed at Jullundur. The report continues as follows:]

“Tænia mediocanellata is very common amongst the Mussulman population of the Punjab, and from reliable sources I am informed that the lower classes amongst them are in the regular habit of eating half-cooked beef; indeed, prefer it so, and it is amongst these people that tapeworm is so prevalent.

“But it is not only thorough cooking that is required to guard soldiers in India from the ill effects of eating measly meat; there is want of cleanliness in the general arrangements of the kitchens and serving of meals, which must offer great facilities for the introduction into the food of Cysticercus.

“Barrack cooks, unless constantly looked after, are utterly careless as to the washing of chopping blocks, tables, dishes, &c. The dish or pot cover on which the meat is placed when raw is often used without washing for serving the piece up for dinner, and I have myself picked up a Cysticercus from the table on which a cook was preparing food. The dangers too of the parasite being conveyed by the cook’s unwashed hands to the plates in which meals are served, and the common practice of using the same knife for cutting up meat, and afterwards, without washing it, for other culinary purposes, must not be overlooked. With good selection and careful feeding there seems to be every probability that Cysticercus would soon almost or completely disappear from our Commissariat cattle. If they were entirely stall-fed and watered from wells there could scarcely be a possibility of infection after their purchase.

“Perhaps with the trench system of conservancy, which will necessitate the growing up crops, a sufficient quantity of root and other green produce may be obtained from cantonment lands set apart for this purpose, to supply green fodder for the cattle.”

The important question as to whether the presence of cysts detected at the root of the tongue could be made available for the purposes of diagnosis was made the subject of special report through the agency of executive Commissariat officers, and they testified to its practical valuelessness in the following terms:

“Jullundur.—No appearance of cyst has been found at the root of the tongues of any of the cattle. A medical officer was asked for assistance in making search for the cysts, but he also found none.

“Rawul Pindee.—It is utterly impossible to discriminate before slaughter, from any outward symptoms, cattle that are cyst infected.

“Every endeavour has been made to discover by close and careful scrutiny before slaughter the cyst-infected cattle, but the result has been in no way satisfactory.

“Sealkote.—All endeavours to discover any symptoms of the infection by examination of their tongues, while the animals were living, have been unsuccessful.

“Mooltan.—The mouth and tongue of a large number of living cattle have been examined before slaughter, but in no single instance has the infection been so detected.

“Dr Ross’s plan of examining the tongues of all animals at time of purchase is not feasible, as they are usually very wild and frightened, and often dangerous to approach.

“Peshawur.—In probably 99 cases out of 100 it is utterly impossible to discover cyst infection in cattle previous to slaughter by examination of their tongues. In only one instance has it been so discovered, and that was from the animal’s having a number of small lumps over the body which were also apparent on the back part of the tongue. When the tongue is infected the ‘cyst’ lies so far at the very root of it that it cannot be seen in the live animal.”

From Mooltan a specially interesting report was made by Dr Alexander Neill, who says:—

“I have carefully examined the mouth and tongue of a large number of living cattle, and of those slaughtered for issue as rations, and in no single instance did I find such cysts. These cattle were healthy.

“In a case that died, and in which cysts existed, I could discover nothing abnormal in or under the tongue.

“If such ‘cysts’ exist, or if such enlargements of the sublingual glands are found, I argue that they are not a diagnostic sign of what is termed ‘cyst infection,’ or more correctly ‘Cysticercus bovis,’ for in the recent outbreak of cattle disease in England, one most prominent symptom of that disease was a bunch of grape-like swelling under the tongue, which in advanced cases suppurated, and to a casual observer would have been called cysts or ‘bags of matter.’

“If such swellings are found in a bullock that is sick, it is merely symptomatic of an inflamed condition of the whole mucous surface of the intestinal canal, and not of any localised disease, such as Cysticercus, the above-mentioned swellings being merely inflamed sublingual glands.

“In the pig the diagnostic sign of swellings of the glands or ‘cyst’ under the tongue is not found in ‘Cysticercus,’ and the disease called ‘measles’ is not ‘Cysticercus,’ but a mere superficial inflammation of the skin and a symptom of fever. ‘Cysticercus cellulosus,’ as its name shows, infects the cellular tissue only of the pig, and cannot be discovered in life by any abnormal condition of skin.

“In ‘measles’ these swellings are found, because intestinal mucous membrane sympathises with eruption on the skin and are then merely inflamed glands, not cysts.”

Dr Neill concludes his report by remarking that the larvæ of the beef tapeworm can “only arrive at maturity in the mucous membrane of horned cattle,” and not in the cellular tissue. This is an error on Dr Neill’s part; but in adducing these instructive extracts from the Government Reports my chief object has been to show the prevalence of Cysticercus in the North-West Provinces of the Indian Peninsula. I may say that a large proportion of my tapeworm-infected patients have been officers from the Punjab, and one of these victims told me that when he superintended the serving out of rations to the troops, “he (and those who acted with him) sent the meat away to be burnt, even when they only detected a single cyst in any given carcase.” It is needless to remark that such a waste of valuable food is altogether reprehensible.

Some people, including not a few of the profession, make light of the occurrence of tapeworm, and I have seen many patients who had been told by their usual medical advisers that the presence of the worms was of little consequence. To account for this wide-spread error there is some basis in the fact that by far the majority of infested persons suffer only the trifling inconvenience arising from the passage per anum of the proglottides; moreover, the less civilised the tapeworm-bearers happen to be, the less are they likely to suffer. The recorded experience of Kaschin, before referred to, where 500 hospital patients, in the Baikal district, had tapeworm, although all of them were being treated for other disorders, affords another argument tending to the same conclusion. On the other hand, amongst Europeans only a small percentage of tapeworm-patients suffer severely. But without trenching upon the symptomatology and prognosis of tapeworm disease, I may remark that I have (in my Manual) summarised the whole facts of cysticercal prevalence within the compass of two brief propositions:—1. The prevalence or the rarity of Cysticerci in cattle in any given country must be determined primarily by the habits of the people; for since the beef measle can only result from the ingestion by the ox of the eggs of the Tænia mediocanellata, it is clear that the degree of infection of cattle will correspond with the facilities offered by egg-dispersion. 2. It may be affirmed that the frequency of this particular species of tapeworm amongst the people occupying any given area will bear a strict relation to the amount of underdone measly beef consumed by the inhabitants.

Another question, and one of great interest to sanitary science, is that which I have raised in reference to the period that nature requires for the destruction of the Cysticerci, or, in other words, for the performance of a natural cure by calcareous degeneration of the parasites. I have shown that all kinds of tapeworm larvæ (measles, bladder-worms, cœnuri, and so forth) have a natural life-epoch assigned to them, and in one of my experiments on a Dutch heifer or young cow I demonstrated that a period of ten months was more than sufficient to ensure the perfect destruction of the Cysticerci of cattle. Moreover, this law or process of natural cure is not limited to cestode parasites, but affects all other kinds of internal parasites in one or other of their juvenile stages of growth. In the flesh of my experimental animal I estimated that there were not less than 12,000 of these degenerated Cysticerci. This positive contribution to our knowledge of the limits assigned by nature to the epoch of larval activity is not merely one of abstract scientific interest, but it has important practical bearings, inasmuch as it points out in what way an entire herd of cattle (known to be measled by the post-mortem examination of one animal previously selected for the purpose, or for that matter, by the rather barbarous act of excising and examining a fragment of the muscle of a living one) may be freed of its parasitic guests; and it also shows how all risk of propagating tapeworm, apart from the question of subjecting the flesh to a certain temperature, may be effectually prevented. The stockowner has but to remove his animals for six or eight months to localities where no fresh infection can occur, when, at the expiration of the time mentioned, all those Cysticerci that existed in the beasts at the time of the transfer will have perished. The flesh of the animals may then be eaten with impunity, whether well cooked or raw. This is an important teaching deducible from experimental inquiry, and I am rather surprised that it has hitherto escaped the notice of persons who, though they affect to ignore the value of scientific researches, are particularly anxious to parade their practical knowledge, which, unhappily, too often proves a mere cloak for ignorance.

The memoir by Giacomini already quoted (p. [65]) affords interesting details respecting a case in which there was a most unusual degree of infection of the human body by Cysticerci. Dr Giacomini instituted a searching comparison between the human measles procured by himself and those of the pig sent to him by Professor Perroncito. In the human Cysticerci he noticed a greater adherence of the capsule to the enclosed measle, and he also observed that while the human measle-heads either displayed thirty-two, or in some few cases thirty-four hooks, in two differently sized circles of fifteen or sixteen each, the pig-measles, on the other hand, carried only twenty-four hooks to the double circle of equal circumference; consequently the hooks appeared to be more crowded together in the human parasite. This fact, Giacomini remarks, does not of itself constitute an essential specific difference, since variations of the kind not unfrequently occur in Cysticerci occupying one and the same host. Even the beef-measle is not necessarily confined to one species of host, since Zenker has succeeded in rearing it in a goat.

Although the substance of the above-recorded conclusions was originally communicated by me, anonymously, to a professional periodical, I have considered this work a suitable medium for a fuller discussion of the subject. Its importance in relation to the public health and the supply of meat-food has not received the attention it deserves.

Bibliography (No. 13).—Balert, B., ‘Die Bandwürmer,’ &c. (pamphlet), 1877.—Bertolus, G., ‘Diss. sur les metamorph. des cestoïdes,’ Montpellier, 1856.—Cobbold, T. S., “On the Production of the so-called ‘Acute Cestode Tuberculosis’ by the Administration of the Proglottides of Tænia mediocanellata” (with Mr Simonds), in ‘Proc. of the Royal Society’ for May 4th, 1865; repr. in the ‘Veterinarian’ for 1865, p. 513.—Idem, “Experimental Investigations with Cestoid Entozoa,” in ‘Linn. Soc. Journ.,’ vol. ix, p. 170; also for July, 1865, p. 141.—Idem, “On Beef, Pork, and Mutton, in relation to Tapeworms,” in ‘Brit. Assoc. Rep.’ for 1865, p. 102, and in ‘Appendix to Treatise on Tapeworms and Threadworms,’ 1st Edit., 1866, p. 73; also in ‘Med. Times and Gaz.’ for Sept. 23rd, 1865, p. 343.—Idem, “Remarks on Entozoa,” in ‘Brit. Assoc. Rep.’ for 1865, p. 102; also on “Cystic Entozoa from Veal and Mutton,” in the ‘Path. Soc. Trans.’ for 1866, vol. xvii, p. 462.—Idem, “Entozoa found in a Westphalian Ham;” report in ‘Athenæum’ for March 27th, 1869, p. 442; also in ‘Brit. Med. Journ.’ for March 20th, 1869.—Idem, “Note on Beef Measles from a Cow,” in ‘Path. Soc. Trans.,’ vol. xvii, p. 463, 1866; also in the ‘Lancet’ for Feb. and August, 1865, p. 249.—Idem, ‘Entozoa,’ &c., p. 235 et seq., 1864; and in ‘Supp.,’ sections iii, iv, v, 1869.—Idem, ‘Tapeworms,’ 3rd Edit. (with 100 cases), 1875, p. 11.—Idem, ‘Manual of the Internal Par. of Domesticated Animals,’ chap. iii to vi, 1874.—Idem, ‘Worms,’ Lectures i to xi, 1872.—Idem, “On the Parasites of our Food-producing Ruminants (Cantor Lectures),” in the ‘Journ. of the Soc. of Arts,’ 1871.—Idem, “On the Entozoa of Abyssinia” (Lecture), in ‘Lancet,’ 1867.—Idem, “Remarks on Eighty Cases of Tapeworm,” ‘Lancet,’ June, 1874.—Idem, “Revised List of Entozoa, with notes and references (the beef tapeworm, No. 15, and the beef measle, No. 25),” in the ‘Veterinarian,’ Dec., 1874, and Feb., 1875.—Idem, (anonymously), “Cysticerci, being a review of the writings of Pellizzari, Tommasi, Perroncito, Lewis, Giacomini, &c.,” contributed to the ‘Lond. Med. Record,’ 1874, p. 642 et seq.; repr. in the ‘Veterinarian,’ Jan., 1875.—Idem, “Notice of a Discussion by Paul, Martineau, Créquy, Delioux de Savignac, Trasbot, and others, respecting the Source and Treatment of Tapeworm,” ‘Lond. Med. Rec.,’ July, 1874, p. 472.—Idem, “Review of the Writings of Oliver, Fleming, Hewlett, Lewis, and others, on the Cystic Disease of Animals,” ‘Lond. Med. Rec.,’ June, 1873, p. 339.—Idem, “Further Experimental Researches with the Eggs of the Beef Tapeworm,” the ‘Veterinarian,’ Aug., 1875.—Idem, “Remarks on Perroncito’s Researches,” the ‘Veterinarian,’ Dec., 1877.—Dardel, A., “Sulla frequenza della Tenia in Savoia,” ‘Giorn. d’Accad. di Med.,’ 1868.—Davaine, C., ‘Traité’ (1. c. Bibl. No. 1), 1860.—Idem, “Les Cestoides,” in ‘Dict. Encyclopédique des Sci. Med.,’ 1875.—Fleming, J., ‘Indian Med. Gaz.,’ 1869.—Fock, H. C. A. L., ‘De Lintworm en het middel om hem mit te drijven,’ Utrecht, 1878.—Fritsch, G., “Zur differentiellen Diagnose von T. solium and T. mediocanellata,” ‘Berliner Klinische Wochenschrift,’ 1874.—Gamgee, J., “Entozoa in Veal and Beef” (Letter on), ‘Lancet,’ 1865.—Giacomini, C., ‘Sul Cyst. cell. hominis e sull Tænia med, contrib. alla studio dei Cestoidi Parrassiti dell’ Uomo,’ Torino, 1874.—Heller, A., “Darmschmarotzer,” in von Ziemssen’s ‘Handbuch der speciellen Pathol. und Therapie,’ s. 598 et seq., 1876.—Hewlett, ‘Health Officer’s Report,’ Bombay, 1870.—Krabbe, H., ‘Beretning om 100 Tilfælde af Bœndellorm hos Menesket iagttagne her i Landet (Aftryk af Ugeskrift for Læger),’ 1869.—Küchenmeister, F., ‘Ueber Cestoden im Allgemeinen und die des Menschen insbesondere, hauptsählich mit Berücksichtigung ihrer Entwickelungsgeschichte, geographischen Verbreitung, Prophylaxe und Abtreibung; specieller Theil. Zittau,’ 1853.—Idem, ‘Parasiten’ (1. c. Bibl. No. 1), 1855, Eng. Edit., London, 1857.—Laboulbéne, A., “Sur les Tænias,” ‘Mém. de la Soc. Méd. des Hôpit.,’ 1876.—Idem, ‘Anat. Pathologique,’ 1879, p. 962.—Letheby, “On Diseased Meat,” ‘Med. Times and Gaz.,’ 1867.—Leuckart, R., ‘Die Menschl. Par.,’ Bd. i, s. 285 and s. 747, 1864.—Levi, “Della freq. della tenia,” &c., ‘Giorn. Veneto di Scienz. Med.,’ 1874.—Lewis, T. K., “A Report on the Bladder Worms found in Beef and Pork” (‘App. B. to 8th Ann. Rep. of the Sanit. Commiss. with the Gov. of India’), Calcutta, 1872.—Masse, E. et Pourquier, P., “Le Tænia inerme et la lardrerie du Bœuf, Nouvelles Expériences,” &c., in ‘Montpellier Med. Journ. Mens. de Méd.,’ p. 220, 1876.—Mosler, ‘Helminthogische studien und Beobachtungen,’ Berlin, 1864. Neill, A., “Letter, forming the fifth of a series of important articles on Cyst-infected Cattle, and on the prevalence of Cysticercus in Beef,” reported by the Inspector General (I. M. D.), in the ‘Madras Monthly Journ. of Med. Sci.,’ Feb., 1873; repr. in the ‘Veterinarian,’ July, 1873.—Nitsche, H., “Untersuchungen ueber den Bau der Tænien,” ‘Sieb. und Köll. Zeitschrift,’ 1873.—Oliver, “Rejections of Ration Beef on account of Cystic Disease” (l. c. supra), ‘7th Rep. of the Commiss.,’ p. 82, Calcutta, 1871.—Perroncito E., “Della panicatura negli animali,” ‘Annali della R. Accad. d’Agricolt. di Torino,’ vol. xv, 1872.—Idem, “Sulla morte del Cyst. cell. delle carni del majale;” ibid., 1872.—Idem, “Ueber die Lebenszähigkeit des Cyst. cell. und anderer Eingeweidewürmer,” ‘Zeitsch. f. prakt. Veter.-Wissenschaften,’ Bern, 1876.—Idem, ‘Della Grandine o Panicatura nell’ Uomo e negli animali,’ Torino, 1877.—Idem, “Esperimenti sulla produzione del cisticerco nelli carni del bovini, coll’ amministrazione di anelli della tænia med. dell’ uomo,” ‘Lo Studente Vet.,’ Parma, 1876, p. 146.—Idem, “Sulla tenacita,” &c., ibid., 1877, p. 194.—Idem, “Esperimenti sulla prod. del Cyst. della T. med. nelle carni dei Vitelli,” ‘Estr. della Annali d. R. Accad. d’Agric. di Torino,’ vol. xx, 1877.—Idem, “On the Tenacity of Life of the Helminths, and their corresponding Larval Forms in Man and Animals,” the ‘Veterinarian,’ July, 1877, p. 457.—Idem (with similar title, including notice of experiments), the ‘Veterinarian,’ Dec., 1877; partly from ‘Osservatore Gaz. d. Cliniche di Torino,’ and from ‘Archivvo per le Sci. Med.,’ vol. i, 1877.—Idem, “On the Tenacity of Life of the Cysticercus in the flesh of Oxen, and on the rapid development of the corresponding T. mediocanellata in the Human Body,” the ‘Veterinarian,’ Dec., 1877, p. 817.—Probstmayr, ‘Jahrb. der Münchener Thierarzneischule,’ 1869.—Rochard, “Note sur la fréquence du Tænia mediocanellata en Syrie, et sur la présence du cysticerque qui lui donne naissance, dans la chaire musculaire des bœufs de ce pays,” in ‘Bulletin de l’Acad. de Méd.,’ 1877, tom. vi, p. 998.—Thudichum, J. W. L., “On the Parasitic Diseases of Quadrupeds used as Food,” ‘Privy Council Med. Officer’s Rep.’ 1865.—Sommer, F., “Ueber den Bau und die Entwickelung der Geschlechtsorgane, von Tænia mediocanellata und T. solium,” in ‘Siebold and Köll. Zeitschrift,’ Bd. xxiv, s. 499, 1874.—St Cyr, “Deux Experiences,” &c., ‘Journ. de l’Anatomie, de Robin,’ p. 504; and in ‘Lond. Med. Rec.,’ by Higgs, vol. i, 582, 1873.—Tommasi, T., ‘Appendice (to Cobbold’s) Parasiti Interni degli Animali Domestice,’ p. 161, Firenze, 1874.—Van Beneden, P. J., “Iconographie des Helminthes ou des vers parasites de l’homme” (Vers Cestoïdes, pl. ii), Louvain, 1860.—Welch, F. H., “Observations on the Anatomy of Tænia mediocanellata,” ‘Quart. Journ. of Microsc. Science,’ vol. xv, 1875.—Zenker, in ‘S. B. Soc.,’ Erlang. iv, s. 71.—Zurn, ‘Zoopathologische und physiol. Untersuchungen,’ 1872.

Tænia solium, Linneus.—This cestode was formerly known as the common tapeworm, but in England it is of far less frequent occurrence than the beef tapeworm. In contradistinction it is best to speak of it as the pork tapeworm. Though only one specimen is usually present, the bearer may entertain several worms of this species at one and the same time. The parasite has been known to science from the earliest times, though possibly not earlier than the measles, or Cysticerci, from which it originates. Hippocrates, Pliny, and Aristotle describe the full-grown worm; and, in regard to the larvæ, some have gone so far as to express their belief that the prohibition of swine’s flesh as food amongst the Jews and other Oriental people, was dictated by sanitary considerations. Weinland has suggested that the Mosaic commandment not to eat pork may have originated in an old popular notion “of the fact that tapeworm sometimes comes from this food.” Weinland’s hypothesis is probably correct, for if one supposes Moses to have been supernaturally informed that pork would produce tapeworm disease, one naturally asks why veal and beef should not also have been prohibited, seeing that these meats also frequently harbour tapeworm larvæ.

A perfect pork tapeworm presents itself to the eye of the observer as a long, soft, white, jointed strobile, which, when alive, elongates and contracts itself with facility. Though commonly spoken of as a single creature, it is a compound of many individuals. These are variously called “cucurbitini,” “zooids,” “proglottides,” “segments,” “links,” or “joints.” When fully grown the segments are capable of detaching themselves and of enjoying a free and independent existence. Very annoying it is to the human bearer to be continually reminded of his unwelcome “guests” as they seek to quit his interior.

The head of Tænia solium is seldom seen in anatomical museums, although the evacuation of pork tapeworms is not of rare occurrence. Placed under the microscope, the head displays a quantity of dark, almost black, pigment granules, which are abundant at the base of the rostellum and in the neighbourhood of the hook-fangs. They are equally present and abundant in the pork measle proper, and in measles derived from the human subject. The cephalic hooks of this cestode are comparatively large, those of the greater circle individually measuring 1/156″, whilst the smaller hooks have a length of about 1/220″.

Fig. 23.—Head of Tænia solium. Highly magnified. After Van Beneden.

The male reproductive organ consists of a number of small vesicles or sacs, in which filiform spermatozoa have been detected, these latter, when ripe, being conducted by a vas deferens into a seminal pouch, from which a canal passes laterally into the penis; the latter organ, in its retracted condition, being lodged within a flask-shaped sheath or cirrhus-pouch. The female organs are somewhat more complicated. They consist of two masses of vitelligene glands occupying a limited space, a small ovarium, a centrally-placed and largely-developed branched uterus, canals of outlet leading from all these organs, and enlargements of the main passages to form internal seminal reservoirs; also, a vaginal canal, which is widened at its termination to form a receptaculum for the curved penis.