Parasites: A Treatise on the Entozoa of Man and Animals / Including Some Account of the Ectozoa

by T. Spencer Cobbold

Part VIII (Ruminantia).

In the matter of parasites this order of mammalian animals stands second in importance. An entire volume of the dimensions of the present would barely do justice to the subject. Although in the article “Ruminantia” in ‘Todd’s Cyclopædia,’ and in my popular treatise on the mammalia, I have described the oxen (Bovidæ) and sheep (Ægosceridæ) as separate families, I shall here speak of their entozoa together; and, at the same time, I shall introduce occasional reference to the helminths of the antelopes and gnoos (Antilopidæ), also of the giraffes (Camelopardidæ), the deer tribe (Cervidæ), the camels, and the llamas (Camelidæ). The parasites of the last family, however, will necessarily stand somewhat apart.

Fig. 61.—Fasciola hepatica. Enlarged. After Blanchard.

Almost all ruminants harbor the liver fluke (Fasciola hepatica). This worm has been found in every variety of the common ox and zebu (Bos taurus, var. Indicus), in the sheep, goat, and argali (Ovis aries, Capra hircus, and G. argali), in the antelopes and gazelle (A. dorcas), in red-deer, roe, and fallow (Cercus elaphus, C. capreolus, and C. dama), and in the two-humped camel (Camelus bactrianus). A closely-allied but much larger species of fluke (F. gigantea) infests the giraffe (Camelopardalis). All these animals are more or less liable to suffer from the “rot” which is produced by these flukes. Into the history of the affection the space at my command does not permit me to enter, but as regards the development of the common fluke I believe the following conclusions to be tolerably well founded. I had long entertained the opinion that our common Planorbis plays the rôle of intermediate bearer, and this view has at length received confirmation.

1. The liver fluke, in its sexually-mature state (Fasc. hepatica), gives rise to the disease commonly called rot; this affection being also locally termed coathe (Dorsetshire, Devon), iles (Cornwall), and bane (Somersetshire). In France it is known as the Cachexie aqueuse, and more popularly as pourriture. In Germany the epidemic disease is called egelseuche, and in a more limited sense either die Fäule or die Leberkrankheit.

2. The rot is especially prevalent during the spring of the year, at which time the fluke itself and innumerable multitudes of the free eggs are constantly escaping from the alimentary canal of the bearer. The germs are thus ordinarily transferred to open pasture-grounds along with the fæces of the bearer.

3. As it has been shown by dissections that the liver of a single sheep may harbor several hundred flukes, and as, also, a single adult fluke is capable of throwing off several thousand eggs, it is certain that any rot-affected flock is capable of distributing millions of fluke germs.

4. Such flukes as have escaped the host per anum do not exhibit active powers of locomotion. Their slight contractile movements, however, serve the purpose of concealing them in the grass, and probably aid in the further expulsion of eggs, which pass from the oviduct in single file.

5. After the death of the escaped flukes the further dispersion of the eggs is facilitated by the subsequent decomposition of the parent worm, and also by its disintegration, partly occasioned by the attacks of insects. It has been calculated that the uterus of a full-grown fluke may contain upwards of forty thousand eggs.

6. By the agency of winds, rains, insects, the feet of cattle, dogs, rabbits, and other animals, as well as by man himself, the freed ova are dispersed and carried to considerable distances; and thus it is that a considerable proportion of them ultimately find their way into ponds, ditches, canals, pools of all kinds, lakes, and running streams.

7. At the time of their expulsion the eggs exhibit a finely segmented condition of the yolk. The egg-contents continue to develop whilst outside the parent’s body, the granular matrix finally becoming transformed into a ciliated embryo, which when set free follows the habit of infusorial animalcules in general by swimming rapidly in the water. The escape of the embryo is effected at the anterior pole of the egg-shell, which is furnished with a lid that opens in consequence of the action of prolonged immersion, aided by the vigorous movements of the contained embryo.

8. The ciliated, free-swimming embryo, at the time of its birth, exhibits the figure of an inverted cone, its anterior extremity, which is broad and somewhat flattened, supporting a central proboscis-like papilla. A small pigment spot placed dorsally, and having the form of a cross, is supposed to be a rudimentary organ of vision. After the lapse of a few days the cilia fall off, the embryo then assuming the character of creeping larvæ (planulæ).

9. Notwithstanding its abridged locomotive powers the non-ciliated larvæ sooner or later gain access to the body of an intermediary bearer, within or upon whose tissues it becomes transformed into a kind of sac or sporocyst. In this condition the larva is capable of developing, agamogenetically, other larvæ in its interior. The sporocysts are highly organised, forming rediæ. According to Willemoes-Suhm, the redia of Fasciola hepatica lives on the body of Planorbis marginata. This organised nurse, which is about a line in length, is the Cercaria cystophora of Wagener. The progeny of this redia consists of armed Cercariæ, which after a time quit the nurse to pass an independent existence in the water.

10. In the cases of some species of fluke there is reason to believe that before the Cercariæ gain access to their final or definitive host they re-enter the bodies of the mollusks. This they accomplish by means of a boring apparatus, and having previously cast off their tails they encyst themselves beneath the surface of the skin. In this new situation they develop into the so-called pupa, which is at length passively transferred with the fodder, or drink, to the digestive organs of the host. In the case of Fasc. hepatica, as probably obtains also with many other flukes, I think there can be no doubt that the Cercariæ pass directly into the bodies of ruminating animals. The circumstance that flukes of this species have been found beneath the human skin shows how considerable are the boring powers of the armed Cercariæ.

In regard to the possibilities of fluke development, that will be best understood by glancing at the constitution of the zoological individual. The sum total of the products of a single germ may be tabulated as follows:—

Zoological individual (Fasciola hepatica).
a.	Ovum in all stages,		First “biotome.”
b.	Ciliated free-swimming embryo,
c.	Nurse, germ-sac, sporocyst (redia),		Second “biotome.”
d.	Active, migrating, tailed larva (cercaria),		Third “biotome.”
e.	Encysted, resting larva (pupa),
f.	Sexually-mature fluke (fasciola).

This is a fair representation of the life-phases of the fluke. The life-phases are rarely less numerous or complicated than here indicated, but Pagenstecher’s researches tend to prove that under certain climatal conditions the number of larval forms may vary considerably. In other words, the fluke individual does not comprise any definite number of “zoöids,” although the kinds of zoöids are limited. I recognise three “biotomes.” The first includes only one temporary, independent life-phase, this is the ciliated animalcule, which I call a “protozoöid.” The second “biotome” may comprise only a solitary simple sporocyst or germ-sac (deuterozoöid), but an almost indefinite multiplication of new and independent germ-sacs, as well as other more highly organised “nurse formations,” may also be developed from the primary sporocyst (secondary and tertiary “deuterozoöid”). The third “biotome” embraces a large but variable number of “tritozoöids” (cercariæ), an equal number, whatever that may be, of “tetartozoöids” (pupæ), and, therefore, also, a similar number of “pemptozoöids” (flukes).

Practically, other curious results arise out of the foregoing considerations. For example, a single sheep may harbor 1000 flukes. Each fluke will develop 10,000 to 40,000 eggs. Each egg may give rise to 370 zoöids. It thus appears that, if all the conditions were favorable, a single fluke might originate between three and four millions of individualised life-forms, whilst the solitary sheep itself would, under the same circumstances, be the means of causing the production of at least 3,000,000,000 fluke zoöids! Happily, no such results as this can possibly occur in nature, since interfering agencies reduce the favorable conditions. However, the balance of parasitic forms from all sources is usually sufficient to destroy thousands of sheep annually. The virulence of rot-epizoöty is entirely due to the presence of conditions favoring the development of fluke larvæ.

As regards the injurious action of this parasite on animals, it is well known that in particular years, in England alone, hundreds, and even thousands, of sheep have been destroyed in a single season. A writer in the ‘Edinburgh Veterinary Review’ for 1861 states that in the season of 1830–31 the estimated deaths of sheep from rot was between one and two millions. This would, of course, represent a money loss of something like four million pounds sterling. As affording additional striking instances of the disastrous effects of rot, I may cite the statements of Davaine. Thus:—“In the neighbourhood of Arles alone, during the year 1812, no less than 300,000 sheep perished, and at Nimes and Montpellier 90,000. In the inner departments, during the epidemic of the years 1853–54, many cattle-breeders lost a fourth, a third, and even three fourths of their flocks.” In like manner our English authority, Prof. Simonds, furnished a variety of painful cases. Thus, on the estate of Mr Cramp, of the Isle of Thanet, the rot epidemic of 1824 “swept away £3000 worth of his sheep in less than three months, compelling him to give up his farm.” Scores of cases are on record where our English farmers have individually lost three, four, five, six, seven, and even eight hundred sheep in a single season; and many agriculturists have thus become completely ruined.

Remarkable periodic outbreaks of this disease are recorded by Simonds as occurring in England in the successive years of 1809, ’16, ’24, ’30, ’53, and ’60; whilst, for France, Davaine mentions 1809, ’12, ’16, ’17, ’20, ’29, ’30, ’53, and ’54, as the most remarkable years. It would be interesting to know how far these outbreaks tally with the similar outbreaks which have occurred in Holland, Germany, and other European districts. The disease was prevalent during four separate years in France and England at one and the same time. This, indeed, is no more than we would naturally expect, considering that the extent of the development of the larval forms must, in a great measure, be dependent upon atmospheric conditions. A warm and moist season would alike prove beneficial to the development of the larvæ and their intermediate molluscan hosts. Their numbers would also multiply enormously; for, as already remarked, the degree of non-sexual production of trematode larvæ within their sporocysts is materially affected by climatic changes. On the other hand, a fine, dry, open season will tend to check the growth and wanderings of the larvæ, and thus render the flocks comparatively secure.

Considerations like these sufficiently explain many of the crude theories which were early propagated concerning the causes of this disease, and in particular, the very generally prevalent notion that water, and water alone, was the true source of the disease. Intelligent cattle-breeders and agriculturists have all along observed that the rot was particularly virulent after long-continued wet weather, and more especially so when there had been a succession of wet seasons. They have likewise noticed that flocks grazing in low pastures and marshy districts were much more liable to invasion than sheep which pastured on higher and drier grounds, but noteworthy exceptions occurred in the case of flocks feeding in the salt-water marshes of our eastern shores. The latter circumstance appears to have suggested the common practice of mixing salt with the food of sheep and cattle, both as a preventive and curative agent; and there can be little doubt that this remedy has always been attended with more or less satisfactory results. The intelligible explanation of the good effected by this mode of treatment we shall find to be intimately associated with a correct understanding of the genetic relations of the entozoon, for it is certain that the larvæ of Fasciola hepatica exist in the bodies of fresh-water snails. As already hinted from Willemoes-Suhm’s observations, it is not improbable that the larvæ are confined to gasteropod mollusks belonging to the genus Planorbis.

The symptoms produced by rot are very striking. When the disease has far advanced it is easy to know a rotten sheep, not only by its very look, but still more convincingly, as I have myself tested, by slightly pressing the hand over the region of the loins. In this region the diseased animal is particularly weak, and the pressure thus applied instantly causes it to wince. At the same time the hand feels a peculiar sensation very unlike that communicated by the spine of a sound animal. In bad cases the back becomes hollow, and there is a corresponding pendulous condition of the abdomen. The spinal columns ultimately stick out prominently, forming the so-called “razor-back.” As Professor Simonds has well observed, in an earlier stage of the disease, “an examination of the eye will readily assist in determining the nature of the malady. If the lids are everted it will be found that the vessels of the conjunctiva are turgid with pale or yellowish colored blood, the whole part presenting a peculiar moist or watery appearance. Later on, the same vessels become blanched and scarcely recognisable.” The skin also becomes harsh and dry, losing its natural tint, and the wool is at length rendered brittle, either becoming very easily detached or falling off spontaneously.

The first thing noticeable in dissecting a rotten sheep is the wasted and watery condition of all the tissues. There is a total absence of that firm, fresh, carneous look which so distinctively characterises the flesh in a state of health. Not only is the rigidity and firm consistency of the muscles altogether wanting, but these structures have lost that deep reddish color which normally exists. When the abdominal cavity is opened a more or less abundant, clear, limpid, or yellowish fluid will make its escape, and the entire visceral contents will, at the same time, display a remarkably blanched aspect. These pathological changes are also shared by the important organ especially affected, namely, the liver. This gland has lost its general plumpness, smoothness, and rich, reddish-brown color, and has become irregularly knotted and uneven both at the surface and the margins, its coloring being either a dirty chocolate brown, more or less strongly pronounced at different parts, or it has a peculiar yellowish tint, which in places is very pale and conspicuous. To the feel it is hard and brawny, and when incised by the scalpel, yields a tough and, in places, a very gritty sensation. On opening the gall-ducts a dark, thick, grumous, biliary secretion oozes slowly out, together with several distomes, which, if not dead, slowly curve upon themselves, and roll up like a slip of heated parchment. On further slitting open the biliary passages, they are found distended irregularly at various points, and in certain situations many flukes are massed together, having caused the ducts to form large sacs, in which the parasites are snugly ensconced. The walls of the ducts are also much thickened in places, and hardened by a deposit of coarse calcareous grains on their inner surface. Mr Simonds says, that the “coats of the ductus hepaticus, as also of the ductus communis choledicus, are not unfrequently so thick as to be upwards of ten times their normal substance, and, likewise, so hard as to approach the nature of cartilage.” Respecting their numbers, the greatest variation exists. The presence of a few flukes in the liver is totally insufficient to cause death; consequently, when a sheep dies from rot, or is killed at a time when the disease has seriously impoverished the animal, then we are sure to find the organ occupied by many dozen, many score, or even several hundred flukes. Thus from a single liver Bidloo obtained 800, Leuwenhoeck about 900, and Dupuy upwards of 1000 specimens. Even the occurrence of large numbers only destroys the animal by slow degrees, and, possibly, without producing much physical suffering, excepting, perhaps, in the later stages. Associated with the above-described appearances, one also not unfrequently finds a few flukes in the intestinal canal, whilst a still more interesting pathological feature is seen in the fact that the bile contained in the liver ducts is loaded with flukes’ eggs. In some cases there cannot be less than tens or even hundreds of thousands. Not a few may also be found in the intestinal canal and in the excrement about to be voided. Occasionally dead specimens become surrounded by inspissated bile, and gritty particles deposited in the liver ducts, thus forming the nuclei of gall-stones. Mr Simonds mentions a remarkable instance, “where the concretion was as large as an ordinary hen’s egg, and when broken up was found to contain about a dozen dead flukes. It was lying in a pouch-like cavity of one of the biliary ducts.”

In respect of treatment we all know that “prevention is better than cure.” Moisture being essential to the growth and development of the fluke-larvæ, it is clear that sheep cannot be infected so long as they remain on high and dry grounds, and even in low pastures they can scarcely take the disease so long as they are folded, and fed on hay, turnips, and fodder procured from drier situations. When once the malady has become fairly developed, internal remedies are of little avail, at least, in view of producing a thorough cure. Palliative treatment may undoubtedly do good, especially in cases where the disease is not very strongly pronounced. The most important thing is the transference of the rot-affected animals to dry ground and good shelter, supplying them, at the same time, with a liberal quantity of manger food, such as beans, peas, and other leguminous seeds. The fodder, of whatever kind, should be frequently changed, and many other hygienic measures adopted, all tending to promote the appetite and general health of the animal. An admixture of salines is a matter of essential importance, especially in cases where the disease is not far advanced. The beneficial effect of salt is one of those few points on which nearly all parties are agreed, and its preservative influence in the case of sheep fed upon salt-water marsh-land has been previously explained. In regard, however, to the legion of remedies which have from time to time been proposed, all I need here say is, that most of them when fairly tested have been found to fail ignominiously. Every year we hear of the adoption, often with enthusiasm, of new so-called specifics, or of ancient medicines whose employment had long fallen into disuse. Thus, for example, in the April number of the ‘Journal des Vétérinaires du Midi’ for 1860, we find M. Raynaud strongly recommending soot, in doses of from one to three spoonfuls, to be followed up by the administration of a grain of lupin for tonic purposes. In like manner, we received from France wonderful accounts of the medicinal virtues of a certain fœtid oleaginous compound, the value of which was put to a fair test by our distinguished veterinarian, Professor Simonds. Having with infinite care and trouble undertaken a series of experiments with the remedy in question, Mr Simonds writes in the ‘Scottish Farmer and Horticulturist’ to the effect that, as a result of his inquiries, he fears “we must conclude that this supposed cure of rot in sheep has proved quite ineffective for good.” The last new “cure” announced is by Mr Robert Fletcher (‘Journ. Nat. Agric. Soc. of Victoria,’ Dec., 1878).

The examination of rotten sheep is not altogether free from danger. Professor Simonds tells us that in August, 1854, “a person of intemperate habits, following the occupation of a country butcher, was employed in skinning and dressing a number of rotten sheep on the premises of a farmer in the county of Norfolk. The sheep were necessarily opened when warm, and while he was so engaged he complained greatly of the sickening smell. The same evening he was attacked with choleraic disease, and two days afterwards was a corpse.” This case is highly instructive and, when taken in connection with the well-known fact that animals affected with the disease putrefy very rapidly, clearly points to the necessity of removing slaughter-houses far away from densely populated localities.

Notwithstanding the above statement, there is little or no danger to be apprehended from the consumption of the flesh of rot-affected animals. On this vexed question we have the strong testimony of the late Dr Rowe, of Australia, who, after leaving the medical profession, became a large and successful stockowner, and devoted himself especially to this question. Dr Rowe, writing from the Goulburn district, said:—“The mere presence of flukes in the viscera of an animal is no proof that it is unfit for human food. For inspectors of slaughter-houses to adopt such a test of wholesome food would be the greatest mistake. It would afford no protection to the public against unhealthy food, would increase the price of animals, and be ruinous to our farmers and graziers. If the consumption of flukey beef and mutton were prejudicial to the health of man, there would be very few people alive in this part of the colony; for, to my certain knowledge, they have had no other animal food to live upon for the last twenty-five years, yet for physical ability I believe they may be favorably compared with the inhabitants of any other part of Australia.” Speaking of his own experiences, Dr Rowe avers that he found the common liver fluke in sheep, cattle, goats, opossums, kangaroos, geese, ducks, and other creatures, but he had never encountered it in men, dogs, or pigs. On the whole I think we may agree with Dr Rowe, in regarding the consumption of the flesh of rot-affected animals as free from danger provided only the meat, be well or even moderately well cooked. It must be borne in mind, however, that an essential objection to its consumption lies in the fact that the watery and otherwise chemically deteriorated flesh is comparatively innutritious. It must also be noted that the meat-supply from fluke-affected animals, as usually sold in the markets, is chiefly derived from animals which have only entered the early stage of the disorder, that is, long before the watery and wasted condition of the muscles has fairly set in.

Respecting the other trematodes I have to observe that Distoma lanceolatum not only infests the liver ducts of cattle and sheep, but also the deer tribe. Its larvæ are likewise supposed to reside in Planorbis marginatus. Still more common and widespread amongst ruminants is the Amphistoma conicum, occupying the paunch. It has been found in the ox, sheep, musk-ox, elk, roe, fallow, red-deer, goat, and dorcas-antelope; also in Cerrus campestris, C. nambi, C. rufus, and C. simplicicornis. Prof. Garrod has also recently shown me examples from the sambu deer of India (C. Aristotelis). Diesing’s A. lunatum, infesting Cerrus dichotomus, is inadmissible. Two other species of Amphistome (A. explanatum, A. crumeniferum) are said to infest the zebu; and I have described another (A. tuberculatum) from the intestines of Indian cattle. An aberrant amphistomatoid entozoon (Gyrocotyle rugosa) has been found in a Cape antelope (A. pygarga). Of more interest, however, is the circumstance that Dr Sonsino has discovered a species of Bilharzia (B. bovis) in Egyptian cattle and in sheep. The eggs of this species are distinctive, being fusiform and narrowed towards either pole.

Comparatively few tapeworms are found in ruminants. Cattle are infested by Tænia expansa and T. denticulata, the former of these two species being also more or less prevalent in sheep, antelopes, and deer. Other alleged species (Tænia fimbriata and T. capræ) appear to me more than doubtful. Unquestionably the common Tænia expansa is capable of giving rise to severe epizoöty among lambs. The privately communicated evidence of Professors Brown and Axe, and published evidence supplied by Messrs Cox and Robertson on this head, are conclusive. Mr George Rugg has also (in a letter to Prof. Simonds, dated Dec. 4th, 1878) communicated the particulars of an outbreak in which “large numbers of lambs perished rapidly” from tapeworms in the intestines, the parasites varying from one to five or six feet in length. This tapeworm (T. expansa) is also very prevalent in Germany. Ruminants, however, both at home and abroad, suffer much more severely from bladder-worms. Of these, Echinococcus veterinorum, Cysticercus tenuicollis, and Cœnurus cerebralis, are not only shared alike by all varieties of cattle, sheep, and goats, but they also infest the deer tribe, antelopes, the giraffe, and even camels. In 1859 I obtained the slender-necked hydatid from a spring-bok (Gazella). Besides these larval cestodes, cattle are very liable to harbor measles (Cysticercus bovis), whilst sheep also entertain an armed Cysticercus (C. ovis). I cannot again dwell at any length upon the source of these immature helminths, but I may remark upon the extreme frequency of measles in Indian cattle. This is explained by the careless habits of the people. They not only consume veal and beef in an imperfectly cooked state, but when suffering from tapeworm no precautions are taken to prevent cattle from having access to the expelled proglottides of Tænia mediocanellata. The subject has already been dealt with in the first part of this work, and also in my ‘Manual,’ quoted in the bibliography. The mutton measle is described under the heading of Tænia tenella. In like manner I must refer to the ‘Manual’ for a detailed account of the gid hydatid (Cœnurus cerebralis). How many kinds of Cœnuri exist it is impossible to say, but I am of opinion that the various polycephalous bladder-worms found by Rose, Baillet, and Alston in rabbits, by myself in a lemur and in a squirrel, and by Engelmeyer in the liver of a cat, are referable to tapeworms specifically distinct from the Tænia cœnurus of the dog.

It was in 1833 that Mr C. B. Rose, formerly of Swaffham, Norfolk, discovered an undoubted example of polycephalous hydatid in the rabbit, the parasite in question bearing a very close resemblance to Cœnurus cerebralis. As the accuracy of Rose’s determination respecting the characters of the hydatid has been called in question, I again invite attention to the original description as recorded in the ‘London Medical Gazette’ for November 9th, 1833. At page 206, vol. xiii, of that periodical, after describing the common Cœnurus cerebralis of the sheep, Rose writes:—“This (i.e. C. cerebralis) is the only species of Cœnurus noticed by authors, but I have met with another. It infests the rabbit, and I have found it situated between the muscles of the loins. It is also met with in the neck and back. This hydatid grows rapidly, and multiplies prodigiously, and being seated near the surface it soon projects, and sometimes forms a tumour of considerable magnitude. When the warrener meets with a rabbit thus affected, he punctures the tumour, squeezes out the fluid, and sends the animal to market with its brethren. I possess a specimen of this species in a pregnant state. The earliest visible state of gestation is a minute spot, more transparent than the surrounding coats of the parent; this enlarges till it projects from the parietes of the maternal vesicle. It continues to enlarge until it becomes a perfect hydatid, attached by a slender peduncle only; even whilst small, other young are seen sprouting from it, and so on in a series of three or four. My specimen exhibits them in every stage of growth, from a minute point to a vesicle the size of a hen’s egg. As I can see no difference in structure between this hydatid and the last-mentioned (i.e. Cœnurus cerebralis), I am unwilling to consider it a different species, for surely a varying locality ought not to constitute a specific character.”

The observations of Rose did not escape the well-known Dutch author, Numan. In a foot-note to his memoir, entitled “Over den veelkop-blaasworm der Hersenen,” he makes the following observations:—“Rose observes that he has found Cœnurus in bladdery rabbits (blaaszieke konijnen) in the skin, and in the cellular tissues of the trunk and extremities. The veterinary surgeon, Engelmeyer, of Burgau, says he has also found the Cœnurus (Veelkop) in the liver of a cat (‘Thierärztliche Wochenschrift van 1850,’ s. 192). These observations differ thus far from those of other writers, according to whom the Cœnurus is only found in the brain and spinal marrow. However, it is not impossible in particular cases that some parasites may have strayed from their ordinary dwelling-places.” Numan seems to have been not a little puzzled to account for these discrepancies, and he was altogether undecided regarding the mode of propagation of Cœnuri and Cysticerci. This will be gathered from the following passage, which I quote in the original:

“Ik moet het onbeslist laten, of de grondbeginsels, waaruit de wormen uit de blaas ontspruiten, als wezenlijke of als zoogenaamde kiemen (gemmæ) zijn te houden, waaromtrent de gevoelens der voornamste Natuuronderzoekers, die zich met de nasporing der blaaswormen hebben onledig gehouden, nog uiteenloopen. Gulliver, door Rose (a. p. pag. 231) aangehaald, houdt ze voor eijeren, in den Cysticercus tenuicollis, en Goodsir, mede aldaar genoemd, spreckt ook van ova bij den Cœnurus cerebralis; doch de laatstgenoemde en Busk houden ze voor gemmæ. Hier wordt voots gewezen op Owen en de meeste onderzoekers van den tegenwoordigen tijd, die het daarvoor houden, dat alle hydatiden zich alleen door gemmæ reproduceren. Rose merkt voorts aan, dat, hetzij men de geboorte dezer ingewandswormen toekenne aan eijeren of kiemen (gemmæ), dit om het even is, wat hunne verspreiding (dissemination) betreft, daar zij ingesloten zijn, waardoor de wijze, hoe zij naar buiten komen en verspried worden, tot dusver een gesloten boek is.”

The idea of Numan that these are strayed forms of Cœnurus cerebralis is not convincing. It must not be forgotten, however, as Leuckart and Numan have both reminded us, that Eichler discovered an hydatid about the size of a goose egg in the subcutaneous tissue of a sheep. This bladder-worm supported nearly two thousand heads. In regard to true hydatids or acephalocysts in ruminants, on which subject I have already dwelt at much length, I may again observe that the Hunterian Museum contains some remarkable examples. In 1854 I obtained Cysticerci from a giraffe, and I have reason to believe that similar bladder-worms infest antelopes and deer.

The nematodes of the ruminants are both numerous in, and destructive to, their bearers, those infesting the lungs being productive of a parasitic bronchitis termed husk or hoose. In cattle the lung-worm (Strongylus micrurus) is particularly fatal to calves, whilst S. filaria attacks sheep, and especially lambs. A larger but less common lung strongyle (S. rufescens) is sometimes found associated with the latter. In 1875 I conducted experiments with the view of finding the intermediate hosts of S. micrurus, and I arrived at the conclusion that the larvæ of this parasite are passively transferred to the digestive organs of earth-worms. The growth and metamorphoses which I witnessed in strongyloid larvæ taken from earth-worms (into which I had previously introduced embryos) were remarkably rapid, and accompanied by ecdysis. The facts were as follows. About the middle of October, 1875, I received from Messrs Farrow, of Durham, a fresh and characteristic specimen of diseased lungs, in which the bronchi were swarming with Filariæ.

In reference to the case itself, Mr George Farrow afterwards informed me by letter that the calf was one of a herd of seven, whose ages respectively varied from four to six months. At the time of his writing (October 20th) the remaining six animals were progressing favorably towards recovery—a result which Mr Farrow attributes to the employment of inhalations of turpentine and savin, combined with the internal administration of tonics. In regard to this plan of treatment, and in reference to the source of infection, he adds:—“I should have preferred trying the inhalations of chlorine gas, but as the patients were so very young and in poor condition, I deemed it advisable to try a milder course of treatment.

“The history of the case is brief. The cattle are on a very dry and well-drained farm, but during the summer there was a great scarcity of water, and they were supplied from a stagnant pool which eventually became dry. This, in my opinion, is where the disease originated.”

Mr George Farrow’s opinion is probably correct, being in harmony with the most recent results of scientific research as made known more particularly by Leuckart. But the facts thus conveyed do not explain the whole truth; or, rather, they convey it only in a very incomplete manner. Professor Leuckart’s experiments were made with several species such as Strongylus armatus of the horse, S. rufescens, S. hypostomus, and S. filaria of the sheep, and S. commutatus of the hare. Still, as regards the strongyles, partial as the results have thus far appeared, there cannot be a doubt that his successes with several allied nematode species form a key by which we may yet unlock and expose to view the entire life-history of that specially obnoxious form under consideration, namely, Strongylus micrurus. To summarise the whole matter in a few words, Leuckart supposes that all these strongyloids require a change of hosts before they can take up their final abode in the sexually-mature state. This he infers especially because their respective embryos display characters very similar to those exhibited by Olulanus. He believes that either small mollusks or insects and their larvæ play the rôle of intermediary bearer. His experiments with the embryos of Strongylus filaria prove that these larvæ can be kept alive for several weeks in moist earth, and that whilst so conditioned they undergo a first change of skin within a period varying from eight to fourteen days. Experiments on sheep, made with these moulting larvæ, led only to negative results. Unless the following facts be accepted, the scientific position remains pretty much where Leuckart left it.

On the 22nd of October, 1875, at 1 p.m., I placed the entire egg-contents of the uterus of a Strongylus micrurus on a glass slide hollowed out in the centre. Probably something like ten thousand ova were thus brought under observation, yet only three were noticed as freed from their shells, probably as the result of accidental rupture. Two of these displayed lively movements. In round numbers the ova gave a measurement of 1/300 of an inch in length by 1/750 of an inch in breadth, whilst the free embryos measured about 1/90 of an inch long, and less than 1/1000 of an inch in thickness. The integument of the embryo displayed neither markings of any kind nor any double contour. The contents of the worm were granular throughout, these granules being crowded in the centre of the body, but scarcely visible towards the head and tail, where for a considerable space (fully 1/300″) the worm was perfectly transparent. No trace of any sexual organs or their outlets was visible. An examination of numerous eggs and free embryos obtained from near the primary bronchial bifurcations (of Mr Farrow’s specimen) yielded the same microscopic results, the only thing worthy of remark being that the embryos from the mucus seemed much more lively than those which, as I supposed, had accidentally escaped their shells.

At 1.30 p.m. I placed some free embryos in two watch-glasses, one containing water and the other saliva, and placed them before the fire. Being called away professionally I found on my return at 3 p.m. that evaporation to dryness had occurred in the interval. All my attempts to resuscitate the embryos by moisture proved unavailing, a result which, though negative, proves how little capable these embryonic creatures are of enduring desiccation. If these facts be confirmed, their practical significance is not without value in relation to the choice of dry pasturage grounds for the rearing of young cattle. I may add that whilst half an hour’s immersion of the dried embryos failed to restore any sign of life, the previous warmth and moisture had caused many more embryos to escape their shells during the time they were placed before the fire.

At 4 p.m. I passed some very rich mould through muslin. Some of this finely sifted earth I placed in a watch-glass, adding a little water to moisten it, and also numerous eggs and free embryos. In a wine-glass and also in a small jar I placed some coarse earth with water added to make thin mud, and to both of these I added, not only eggs and embryos, but also portions of the reproductive organs of the adult female worms.

On the 23rd of October, at 2 p.m., I examined the contents of these vessels. All the embryos in the vessels containing the coarse earth were dead, but several were found alive in the watch-glass containing the fine moist mould. Structurally these latter had undergone no perceptible change beyond a somewhat closer aggregation of the somatic granules.

Although the embryos in the coarse wet mud had perished, the eggs with unhatched embryos appeared to have retained their vitality. Of this fact, indeed, I subsequently obtained abundant proof; and I also satisfied myself that the death of the embryos had not resulted either from the coarseness of the earth or from excessive moisture, but from the presence of numerous shreds of the uterine tubes which I had somewhat carelessly added to the vessels. Previous experiments, conducted many years back, had indeed taught me that few if any nematoid larvæ can resist the fatal action of putrid matter, however slight the putrescence.

Having removed the offending shreds, I next placed a quantity of living ova together in the earthenware jar, and allowed the earth-contents to become much drier by evaporation before the fire. I also left others in a watch-glass, which was placed under a bell-jar enclosing several ferns.

On the 25th of October I removed particles of the moist earth, altogether weighing about two grains, and, on submitting them to microscopic examination, had the satisfaction to observe about a dozen living embryos, some of which exhibited very lively movements. There was not the slightest indication of putridity; nevertheless, I noticed several shreds of the adult worms whose presence had been accidentally overlooked, and, curiously enough, all the embryos subsequently removed from the immediate neighbourhood of these decomposing shreds of tissue were almost motionless and apparently in a moribund condition. On examining the contents of the watch-glass placed under the fern shade, I noticed several points of interest. First of all the earth contained strongyle embryos, such as I had seen before. Secondly, the surface of the mould was being traversed by three or four briskly-moving Thysanuridæ, hunting about with all that restless activity which Sir John Lubbock has so well described. Thirdly, in marked contrast to the behaviour of these I noticed several slow-moving Acaridæ, apparently also employed in searching for food. And lastly, while thus engaged, the surface of the mould in the centre of the deep watch-glass was suddenly upheaved, by which I was at once made aware of the presence of another most welcome and unexpected intruder. In short, an earth-worm had crept from the dry mould in which the ferns were growing, and had taken up its temporary abode in the soft moist experimental-earth contained in the watch-glass. When contracted, this Lumbricus terrestris was barely an inch in length. On placing it under the half-inch objective glass, I noticed a single embryonic strongyle adhering to the skin, but not firmly, and evidently only in an accidental way, so to speak. It was clear to me that it possessed neither the intention nor the power to penetrate the chitinous integument of the earth-worm.

Having in the next place removed the Lumbricus with a pair of forceps, and having washed it under a current of water, I snipped off the lower end of the body, and allowed some of the intestinal contents to escape on a clean glass slide for separate microscopic examination. Immediately, to my satisfaction, I found that the fæcal contents displayed a large quantity of my strongyle ova, enclosing still living embryos, and in addition several free embryos presenting characters which declared that they were from the same source. Clearly they had been ingested by the earth-worm along with its ordinary food. One or two of the embryos were conspicuously larger than their fellows, but the structural changes they had undergone were not so marked as to lead me for a single moment to associate them with any of the various sexually-mature worms which have been described as normally infesting the earth-worm. I had no doubt whatever that such slight structural changes as were now discernible had resulted from growth and development consequent upon this accidental admission into the body of the intermediate bearer which might or might not prove to be its legitimate territory. It will be seen that subsequent observations tended to affirm the truth of this view. I made a careful examination of one of these larvæ, whose active movements were such as to render the process exceedingly tedious. The earth-worm itself (or rather its unequal halves) was placed in a fresh watch-glass containing ordinary mould. The larvæ or embryos obtained from the earth-worm now measured about 1/80 of an inch in length, their heads exhibiting a short and simple chitinous buccal tube, whilst their tails were somewhat more pointed and bent upward. The somatic granules were more crowded, rendering the position of the intestinal tract more marked, though, as yet, the differentiation gave no indication of the formation of a distinct intestinal wall. There was no perceptible increase of thickness of the body of the embryos. The results thus far naturally encouraged me to procure some fresh earth-worms for experimental purposes.

On the 26th of October I found that the halves of the earth-worm were alive, and I left them undisturbed in rather dry mould, freshly added. To a watch-glass containing newly sifted earth and embryos I added a fresh garden-worm, which was rather sluggish from the cold; and in the original jar I placed another smaller and very active earth-worm obtained the same morning. Finding the soil in the jar congenial, this lumbricus soon buried itself. Another and larger earth-worm subsequently added refused to follow this example. It was therefore removed from the jar. Believing the fine and artificially prepared soil to be still much too moist, I caused further evaporation; and I afterwards found that the thicker the mud the more suitable it proved as a residence for embryonic nematodes and earth-worms alike.

On the 27th I found the small earth-worms in the jar burrowing freely and throwing up fæcal casts. From one of my watch-glasses the worm had escaped, its place being occupied in the meantime by an actively crawling Julus. I put a second Julus, obtained from the mould in the fern jar, to form a companion (in view of other experiments), and I also added a fresh earth-worm, covering all by another inverted watch-glass, which I thought would prevent their escape.

In the next place I examined the halves of my original experimental earth-worm. They were scarcely capable of motion, but retained a certain amount of vitality. The tail was the more active half, and unfortunately it was soon afterwards lost. Carefully washing the superior half, and transferring its contents to a glass slide, I immediately detected under the microscope a large number of embryos. They were in a state of marked activity, the largest having increased to about 1/50″ of an inch in length, whilst their structure had become correspondingly advanced. Here, again, there was no room for doubt as to their source, especially as they individually displayed different degrees of organisation, all answering to one and the same embryonal type. I now observed a distinct œsophagus, the rest of the intestinal tract being still more conspicuous than heretofore, though, as yet, no true cells marked the limitation of the stomach and chylous intestine.

After an hour’s immersion in cold water some of the larvæ became much less active, whilst others were motionless, so that I feared all were about to perish. In the hope of keeping a few of them alive I now added to the slide some finely sifted grains of mould, placing the slide under a small bell jar which protected some of my ferns. The remains of the moribund earth-worm were also covered with mould.

Other larvæ, derived from the earth-worm, were placed on the moist pinnæ of a living fern-frond which supported small drops of water, for by this process I hoped in some measure to imitate the dew which naturally condenses on the grass and fodder of our low-lying fields. At 3.15 p.m. of the same day (27th) I also examined a fresh worm pellet from the jar, and found it to contain living strongyle embryos, which as heretofore had not exhibited the slightest advance either in respect of size or structure.

At noon on the 28th I again sought for the larger larvæ, first of all on the slide covered with fine earth, and afterwards within the remains of the upper half of the original earth-worm. On the slide I could detect none, but within the intestine of the worm there were still two living larvæ left, whose characters corresponded precisely with the largest that I had previously obtained from the same source only the day before. They had undergone, however, no further change in structure, and their measurements remained precisely the same.

At 12.30 p.m. I snipped off two or three of the terminal fern-fronds on which I had placed a few advanced larvæ. On examination under the half-inch objective I immediately detected one of the larvæ cruising about most actively. On adding a drop of water it soon rushed across the field of the microscope, its movements being thoroughly eel-like. The size of this larvæ had so much increased that it was now visible to the naked eye, measuring, indeed, as much as 1/30 of an inch from head to tail. Moreover, its organisation had advanced in a marked degree. Thus, the digestive organs were better defined, and on one side of them there appeared a regularly arranged congeries of cellules, forming the commencement of the reproductive organs. As yet, however, I could not pronounce as to the sex.

At 1.45 p.m. I again examined a few grains of earth from the jar, when I at once noticed five or six active embryos whose structure failed to show the slightest advance upon that originally described. It was evident that the jar contained thousands of them; and since no ova were found, it became probable that all their embryonic contents had escaped to swell the number of free larvæ, leaving their very delicate envelopes to perish. I think I had hit upon the most suitable degree of moisture favorable to this result.

In the next place I sought for the earth-worm that had been placed in the infested soil between two watch-glasses. It had escaped. This obliged me to transfer the mould to a rather wide-mouthed and open phial, in which four more fresh lumbrici were placed. I feared the closing of the bottle would be detrimental.

Later in the day I selected an earth-worm which had not been exposed to strongyle infection, but which was in a moribund condition. In the intestine there were several free nematoids and also several psorosperms of the genus Monocystis, so well illustrated by E. Ray Lankester. As to the nematoids, which were filariform, they neither corresponded in size nor structure with my strongyle embryos.

At 1 p.m. on the 29th I renewed my examination of the larva removed from the fern-pinnule. It showed a further stage of growth, the male character of the reproductive organs having become apparent. The now tolerably well-formed vas deferens had pushed the chylous intestine on one side, whilst a series of caudal rays, five on either side, supported two narrow membranous wings, which represented the lateral lobes of the hood of the adult strongyle.

At 1.30 p.m. I submitted the intestinal contents of four fresh earth-worms removed from my garden to microscopic examination, but no nematoids were found in any one of them.

About 2 p.m. I removed another large and active strongyle larva that had been reared on another fern-pinnule. It was of the same size as that previously described, but was in the act of changing its skin. It was then put aside along with the other worm under the glass shade.

At 3 p.m. I intended to have examined one or more of the earth-worms placed in the open-mouthed phial, but all had escaped and buried themselves in the fern-mould out of reach.

At noon on the 30th I renewed my examination of the two large larvæ whose developmental changes I had been instrumental in producing from the time of their escape from the egg-coverings. I saw no reason to doubt that the sequence of changes thus far noticed referred to the species of parasite under consideration. Both larvæ were active, but the moulting one had now completed its ecdysis. Its sexual distinctiveness had become yet more pronounced by the formation of two rather short and stout spicules, the point of the tail displaying a very minute awl-shaped projection. The lateral membranes had not visibly increased in size. One of these larvæ, the first under observation, now perished from the injuries sustained during inspection.

Again, and later in the day, I sought to clear up any doubts that might still suggest themselves respecting the source of these larvæ, by once more submitting the intestinal contents of two fresh and uninfected earth-worms to careful scrutiny. In the first worm no parasite could be found, and in the second only one minute nematoid; its organisation, which was sexually incomplete, neither corresponded with my strongyle embryos, nor, so far as I could judge, with Goeze’s Ascaris minutissima microscopica (the Anguillula lumbrici of Diesing and others), nor with Dujardin’s Dicelis filaria. It was a very long and narrow creature, but I lost it whilst attempting to secure an accurate measurement. I should say it was about 1/50th of an inch in length, and not more than 1/1500th in breadth. I made a rough outline sketch of it.

In view of further observations I now placed five more earth-worms in the jar containing strongyle embryos, and I also placed six others in the phial which contained coarser mould, and only a comparatively small number of the original strongyle embryos. The phial was closed with a cork and half buried in the fern-mould of one of my larger Wardian fern-pans. Before this transfer was made I again took an opportunity of ascertaining by microscopic evidence that the embryos lodged in the coarse and fine mould had none of them made the slightest advance in organisation. The worms placed in the jar immediately proceeded to bury themselves.

At noon on the 1st of November I sought to get further results from the only large free larva which now remained to me (for the fern-pinnules on which the larvæ were originally placed had dried up and no third specimen could be discovered). Structurally the larva presented no advance. It therefore appeared to me necessary to place it under new conditions in view of exciting further progress towards sexual maturity and adult growth. To transfer it to the bronchus of a living calf would, of course, have been the crucial experiment, but the hopelessness of getting any satisfactory result from this solitary transfer deterred me from the attempt. On a larger scale, with many larvæ, a positive issue would of course prove decisive. Accordingly, the only thing I could do, in partial imitation of nature, was to try and induce some further changes by placing the larva in human saliva, kept warm artificially. As a first step I immersed the creature in a little of the secretion added to the glass slide, when it immediately displayed very lively movements, such as could only be fitly described as frantic. This encouraged me to replace the slide under one of the fern shades without applying any additional heat. I then left it.

At 12.30 p.m. I selected three of the eleven worms lodged in the infested earth, namely, two from the jar and one from the closed phial, and made a microscopic examination of their respective intestinal contents. In one of the worms from the jar I found several embryos clearly referable to my strongyles, their structure showing scarcely any advance upon that exhibited by the embryos in the mould itself. The weather was now excessively cold and the larvæ were motionless; nevertheless, the application of warmth showed that they were by no means dead. The fæcal matter obtained from the worm that had lived in the phial displayed an immense number of infusoriæ (Bacteria) which rushed about rapidly over the field of the microscope. No other signs of life were detected.

On the 2nd of November I found my solitary strongyle larva alive, but its movements, though active, were by no means so active as on the previous day. No fresh structural changes had occurred.

At noon on the 3rd the larva at first lay almost motionless in the now thick and ropy saliva; nevertheless, on applying a thin glass cover its movements became tolerably vigorous. During its quiescent state I succeeded in getting a good view of the caudal rays and other imperfectly developed organs, of which I retain figures.

Having now satisfied myself that other new conditions were necessary to enable the larva to arrive at sexual maturity, I sought to transfer it to a glass tube filled with fresh saliva. This transfer was a matter of difficulty. After passing the thick ropy saliva into the tube, I examined the slide and found that the larva was gone. I concluded it was in the tube, which, in order to keep the contents warm, I subsequently carried about concealed in my under-clothing during the day and placed in my bed during the night. This increase of temperature, however, caused decomposition of the saliva; so when next day I diligently sought for my experimental nematode it was nowhere to be found. Thus terminated my observations on the first set of embryos, which had enjoyed their temporary sojourn in the intestinal tract of the earth-worm, and which had certainly afterwards undergone a series of marked structural and morphological changes, accompanied with ecdysis.

The weather had now been for several days exceedingly cold, but on the 4th a favorable change set in, which led me to hope that I might be able to verify the facts above recorded. Accordingly, as a new point of departure, I re-examined the fine mould, and at once found my embryos in a high state of activity. The mould, however, appearing too moist for the earth-worms, I permitted further evaporation before closing the jar with a glass cover. Four days subsequently I examined the intestinal contents of two of the earth-worms. In one of these, an inch in length, no parasite of any kind could be detected; but in the other, which was beyond three inches in length, there were numerous Opalinæ besides several strongyle embryos, the latter presenting characters not visibly in advance of those still living in the mould. All of them were motionless, as if they had not got over the shock produced by previous cold. Moreover, the weather had again become cold, and thus, when I again inspected my experimental embryos living in the jar, I also found them motionless, so different from their behaviour on the 4th. However, since a further result with the earth-worm embryos appeared possible, I placed some of the fæcal matter, already ascertained to contain a few of them, on the fronds of a thoroughly moist and dew-covered Asplenium bulbiferum. This plant was in a fern-pan which had the advantage of considerable fire-warmth during the day. When, however, on the 15th of November, I examined the fæcal earth removed from several of the pinnules, I failed to find any of the embryos. Possibly they had wandered, for the entire frond was covered with dew-drops, which was not the case with the fern that I had previously experimented on with such satisfactory results. At all events, whether they had wandered or had perished, their apparent absence in no way affects my previous record; and the more so since only a few had been observed in the fæcal matter. The smallness of the number found in the earth-worm was also readily accounted for. Thus, when at 1.30 p.m. on the 15th I made a diligent search for embryos in several grains of the fine mould, not a single young strongyle could be detected. Possibly the frost of the previous night had killed them. The earth-worms were still alive and in good condition.

In conclusion, I may observe that every experimenter with helminths is well aware how unfavorable the winter season is for this kind of research. If a repetition of this inquiry in the spring or summer should confirm these results, it will prove a clear and substantial addition to our knowledge of the development of the strongyles. Meanwhile, I think that the data above given render it highly probable that the larvæ of the hoose-producing strongyle (S. micrurus) are passively transferred to the bodies of setigerous annelids, which are thus called upon to act as intermediate hosts. If this be so, it is further certain that important structural changes with ecdysis follow after their escape from the earth-worms or other annelids, moisture, dew, or water being essential to the penultimate stage of growth. Final passive transference, either with fresh fodder from swampy grounds, or, it may be, from pond water, ultimately enables them to acquire their definite sexual form, size, and other adult characteristics.

According to Mégnin it is not the Strongylus filaria, but a hitherto unknown and totally distinct species (Strongylus minutissimus) which occasions pneumonia in Algerian sheep. In England the parasitic bronchitis affecting sheep is generally called the “lamb disease.” This is unfortunate, because many other parasites prove destructive to lambs. One of the most injurious species is Strongylus contortus, infesting the true stomach, whilst S. hypostomus, occupying the small intestines, is almost equally obnoxious to the ovine bearer. By Leuckart and others this last-named worm is retained in Dujardin’s genus Dochmius, in which genus another species occurs (D. cernuus). This worm is quite distinct, but not readily distinguishable by the naked eye alone. It occasionally occupies the upper part of the colon, as well as the lower end of the small intestine. A rarer intestinal worm in lambs is the Strongylus filicollis. Several other strongyles infest the ox (S. radiatus, S. inflatus, S. gigas), goat (S. venulosus), and stag (S. ventricosus).

As showing the extraordinary prevalence and destructiveness of entozoa in certain countries, I will adduce an instance in which my opinion was requested and given some five years since. My informant stated the case somewhat in the following manner:—On a farm in New South Wales, and lying about 200 miles to the north-west of Sydney, on the Trafalgar tributary of the Macquarie river, out of a flock of about 8000 sheep no less than 1200 have perished. In many instances post-mortem examinations were made, worms appearing in all cases to be the cause of death. There were four kinds of parasites present. The most numerous were red and white, “marked like a barber’s pole.” These occurred chiefly in the fourth stomach and commencement of the duodenum, but some were found throughout the entire length of the small intestine. A second set comprised small black worms, resembling needles, scattered only in the lumen of the intestines. The third set were tapeworms, each being several fathoms in length. The fourth set was made up of white threadworms, individually measuring two inches in length. These occupied the bronchial tubes, and were characterised by my informant as “the most deadly of all.” Without the aid of specimens I at once recognised these brief diagnostic characters as severally referring to Strongylus contortus, Dochmius hypostomus, Tænia expansa, and Strongylus filaria.

What the inquirer desired at my hands was “full information respecting the general principles to be carried out in view of the prevention of this parasitic disease, regard being had to the difficulty of finding any food but pasture, to the number of animals to be treated, and to the not unfavorable circumstance that the run is divided by fencing to a great extent.” I was also requested to explain the best modes of treatment, being at the same time informed that turpentine drenchings had already been employed with only “partially effective” results. I was also expected to give numerous and varied formulæ, to be tried in succession, supposing the first should fail. Of course, it should have been known that I neither prescribe medicines nor accept fees in respect of animal patients; but, as in this instance my opinion was permitted to assume the form of a “written scientific report,” I was pleased to have an opportunity of commenting freely and fully on the significance of the facts submitted. My advice took the form of a long report, which might here be usefully given in extenso were it not somewhat of the nature of a private and privileged communication. I have no doubt that the stockowner would be pleased that I should utilise his remarkable “case” for the benefit of agriculturists and others; but it is for him to publish the “opinion” as it stands, should he think fit to do so.

Practical men, on reading the few foregoing particulars, will perceive that one of the principal obstacles to success in cases of this kind lies in the circumstance that artificial food can only be procured with difficulty. Where the source of the disease is associated with the pasture-supply, any treatment, however effectual for a time, can only be followed by partially satisfactory results.

The destructive powers of any one of the above-mentioned parasites being sufficient to produce a fatal lamb-disease, it is clear that when two or more of these particular species attack their victim in considerable numbers, the ovine-bearer has little chance of recovery. The intestinal strongyles, by means of their oral armature, behaving as veritable leeches, will, if not expelled in good time, produce a rapidly fatal anæmia, precisely in the same way as the human Anchylostomum of the tropics.

The worst of dealing with this sheep-parasite is that it will not succumb to ordinary doses of salines like the stomach strongyle; moreover, the little leech-like wounds will probably bleed after the parasites have been compelled to abandon their hold. Prevention is better than cure. Accordingly, I sought to explain the origin of these creatures, and in what possible ways the germs of the various species could be destroyed, or at least limited in numbers.

As to the drugs and inhalations to be employed, it would be difficult to advise any more effective than those commonly in vogue, the great thing being to effect changes of pasture and ground, to look to the purity of the water-supply, and to supply the best kinds of nourishment after active treatment. The diseased animals should, from the very first, be separated from their companions, because the amount of germ distribution is thereby greatly lessened. They should be at once drenched or treated by inhalation (as the parasitic nature of the attack requires), and the enclosure in which the animals have been temporarily housed should be thoroughly scoured with boiling-hot water impregnated with salt.

The nomenclature of the parasitic diseases of animals is excessively vague. Thus, apropos to the case above recorded, I may mention that an American veterinary practitioner appeared to be much shocked that I should have had the temerity to speak of four distinct kinds of lamb-disease. It is in this way that practical men often commit serious mistakes by rolling together disorders that are totally distinct. If it were true that epizoöty in lambs is exclusively due to Strongylus filaria, then professionals might aptly speak of the parasitic bronchitis of young sheep as lamb-disease; but we now know that several other helminths prove terribly fatal to lambs, occasioning death in totally different ways. In one set of cases the animals are asphyxiated; in another set they become fatally anæmic; and in a third set they perish from the severity of nervous reflex irritations. Lastly, it may be remarked that, in view of the successful management of the parasitic disorders of animals, the veterinary practitioner must necessarily be guided by the same general principles as the physician. For myself, I may say that I have hitherto designedly withheld many practical hints which a long experience with human patients suggested, not wishing to appear to dictate to those who are constantly seeing animals. However, since (contrary to my own wishes) it has happened that both professional men and agriculturists have not only invited me to give opinions, but have, at various times, asked me to prescribe, it seems there can have been no impropriety in publishing my views on this subject. Certainly I have had no professional motives to serve.

Of the few non-strongyloid nematodes, one of the commonest is Trichocephalus affinis. I have obtained this worm from the giraffe, and the parasite may be said to infest all ruminating animals, not excluding even the camels and llamas. As before remarked, the whipworm has been known to produce severe symptoms in man, and it occasions “scour” in the sheep. The eyes of cattle are occasionally infested by Filaria lacrymalis and F. papillosa. The last named is the common eye-worm of the horse. On Feb. 27th, 1875, Dr Edward L. Moss, of H.M.S. “Alert,” brought me three examples of a nematode which I referred to Filaria terebra. Dr Moss obtained these parasites in 1874, during the time that he had charge of the Naval Hospital at Esquimalt, Vancouver’s Island. They occupied the abdominal cavity of the black-tailed deer (Cervus columbianus). The worms were mostly found lying amongst the coils of the small intestine. They were not attached to the peritoneal membrane. Dr Moss had shot seventeen deer in all, the males and females being in about equal proportion; nevertheless, not one of the bucks showed any trace of the presence of these entozoa. This absence of parasites in the male deer is noteworthy. Hitherto the worm appears to have been observed in the red deer (C. elaphus), and by Natterer in three species of American roe (C. rufus, C. simplicicornis, and C. nambi). Two of the worms measured each about 21/3″ in length, the third exceeding 3″. They displayed in profile two prominent oral papillæ. Probably there were four of these processes, such as Dujardin described in his Filaria cervina, which, according to Diesing, is a synonym. They all possessed spirally twisted tails.

Amongst the arachnidan parasites of ruminants having entozoal habits are Pentastoma denticulatum and P. constrictum. The former larval worm is excessively common in cattle, sheep, deer, and antelopes. According to Rhind, the adult worm (P. tænioides) also infests the sheep. The P. constrictum has hitherto only been found in the giraffe. On the 10th February, 1859, I obtained numerous examples (P. denticulatum) from a bubale (Antilope bubalis) which died at the Zoological Society’s Gardens. The greater number occupied the surface of the lungs and intestines; some few, however, were enclosed in cysts beneath the pleura. In the spring of 1860 I also procured several specimens from the abdomen of a cape guevi (Cephalopus pygmæus).

The ectozoa of ruminants have received much attention, but I can merely indicate the known forms. Following Mégnin’s classification we have three well-marked varieties of the acarine genus Sarcoptes (S. scabiei, var. ovis, var. capræ, and var. cameli), two varieties of Psoroptes (P. longirostris, var. bovis and ovis), and Chorioptes spathiferus. This last is the true mange mite of the ox (or Symbiotes bovis of Gerlach). A variety of the follicle mite infests the sheep (Demodex folliculorum, var. ovis). Numerous species of tick (Ixodidæ) have been more or less fully described. Of these we have the Carapartos of the Portuguese (Ixodes bovis), attacking cattle; the I. reduvius, attacking sheep; the I. plumbeus, said to attack lambs; the I. albipictus and I. unipictus, found on the moose-deer. Probably this species also attacks cattle. A most horrible arachnidan is found on camels. I allude to Galeodes araneoides belonging to the Solpugidæ. This parasite will bite severely any person who attempts to dislodge it from the bearer. Turning to the insects, we find ruminants liable to be annoyed alike by flies (Diptera), fleas (Aphaniptera), and lice (Hemiptera). Various species of four different families of flies are apt to prove troublesome. Of the Œstridæ, attacking the ox, we have Hypoderma bovis, whose larvæ form tumours or warbles on the back; also H. lineata, Dermatobia noxialis, and Cephenomyia bovis (mihi). The larvæ of the latter reside at the root of the tongue and adjacent parts. In the sheep we have Œstrus ovis, Œ. purpureus, and Hypoderma lineata. Various species also attack goats and antelopes. Dr Kirk presented me with specimens of Œstrus from the frontal sinuses of a harte-beest or caama, and they have also been obtained from the sassabe, the saiga or colus, from the gnoo, and from the brindled gnoo, kokoon or gorgon. Mr Charles Danford presented me with several bots from an ibex. One or more species of Hypoderma have likewise been removed from the gazelle and other antelopes. The deer tribe are much attacked by bots. In the red deer we have Hyp. actæon and H. diana, a species also infesting the elk. The throat-grubs are Ceph. rufibarbis and Pharyngomyia picta; another species, also occurring in the fallow deer, Ceph. ulrichii, infests the elk, and C. stimulator the roe, the last-named deer being also infested by Hyp. diana. A throat-fly infests the reindeer, which is also frequently attacked by Hyp. tarandi. Specimens of the latter worm have been obtained by Dr Murie at the Zoological Gardens. The Hunterian Museum also contains these and other species of bots, presented by myself in Mr Andrew Murray’s name. A subcutaneous bot has been found in the musk-deer. A throat-bot (C. maculata) infests the dromedary.

In regard to the so-called free dipterous parasites and other noxious insects that attack ruminants, their name is legion. One of the worst is the tsetse (Glossina morsitans), immortalised by Livingstone. Of the Muscidæ we have the ox-fly (Musca bovina), the sheep-fly (M. cæsar), and the executioner (M. carnifex). Of the Tabanidæ we have T. bovinus and T. autumnalis, Chrysops cæcutiens, and the allied Asilus crabroniformis (Asilidæ). Amongst the specially noxious insects must also be placed Stomoxys calcitrans and Rhagio columbaschensis. This fly proves fearfully destructive to cattle in Hungary and Servia. Lastly, I can only further mention the common Melophagus ovinus. This is nothing more than a gigantic louse, which from long use agriculturists and veterinarians persist in calling the sheep-tick. It belongs to the Hippoboscidæ, the members of which family only attack quadrupeds and birds. As regards the lice (Anoplura), I have to mention Hæmatopinus vituli of the calf, H. eurysternus of cattle, and H. stenopsis of the goat; also Trichodectes scalaris, T. sphærocephalus, and T. capræ. These infest the ox, sheep, and goat, respectively.

For some account of the protozoal parasites (Psorospermiæ, &c.) infesting the flesh of ruminants I must refer the reader to Book I, Section IV, [Part VI] of this treatise.

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