A system of practical medicine. By American authors. Vol. 2

by Unknown

INTESTINAL WORMS.

BY JOSEPH LEIDY, M.D.

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All animals, except in general the simple cell-forms constituting the sub-kingdom of protozoa, under ordinary circumstances are more or less liable to be infested with others, called parasites, which commonly live at the expense of their hosts, frequently with little or no inconvenience, but often causing discomfort and suffering even unto death. Parasites are distinguished as external and internal, the two being mostly of a widely different character. The former chiefly pertain to the division of arthropoda, or animals with jointed limbs, as exemplified by lice, fleas, and flies of the class of insects, mites of the class of arachnides, and epizoans and isopods of the class of crustaceans.

Internal parasites, from their usual habitation named entozoa, are commonly observed in the intestines of animals, and hence their distinction as intestinal worms. The name has proved to be appropriate, for investigations have shown that most entozoa, observed from time to time in other parts of the bodies of animals, pass part of their life in the intestinal canal of the same or of some other animal.

By far the greater number of entozoa are peculiar animals, constituting the chief part of the scolecides, an extensive group of the sub-kingdom of vermes or worms. Of this group they comprise the orders of CESTODES, or tape-worms; the ACANTHOCEPHALI, or thorn-headed worms; the TREMATODES, or fluke-worms; and the greater portion of the NEMATODES, or thread-worms. Many entozoa also belong to the protozoa, but these, so far as relates to man in a medical point of view, appear unimportant, and will therefore not here enter into consideration.

In the course of their life entozoa undergo changes of form and condition, and pass these in different organs of the same or of different animals, and it may be for a brief period externally or in a non-parasitic state. In many instances, as in the tape-worms and the fluke-worms, the transformations accompanying the changes are of so extraordinary a character that until their life-history was investigated the successive metamorphoses were viewed as distinct animals. Mostly, the entozoa pass one stage of existence within the intestine of some animal, and another stage in different organs of other animals. Many, perhaps most species, in each stage are peculiar to one or a few nearly-related animals, but others of the same kind infest a number of different animals. The animals infested by the same parasite may be remotely as well as nearly related. Thus the Tænia saginata, or beef tape-worm, in the mature state lives in the small intestine of man only, but in its juvenile or larval condition in the flesh meat of the ox. The Tænia elliptica, the common tape-worm of the intestine of the dog, in the larval condition lives in the louse of this animal. The liver-fluke, Distomum hepaticum, occasionally found in the liver of man, but of common occurrence in the sheep, to which it proves so destructive in the affection known as rot, in the juvenile condition lives in a little fresh-water snail of the genus Lymneus. The guinea-worm, Filaria medinensis, which in the mature state is found beneath the skin of man, in the larval condition inhabits the minute crustacean cyclops of stagnant waters.

As would be reasonably supposed, entozoa commonly gain access to their hosts through the food and drink, though in the case of aquatic animals they also obtain entrance directly through the integument from the surrounding medium. So long as they remain in the intestinal canal they may occasion little trouble or inconvenience. When they are numerous in this position or proportionately large, according to their peculiar nature they may produce more or less suffering and even the most serious consequences. Generally, however, it is when they occupy other positions, to which they have migrated from the intestine, that they induce aggravated symptoms proportioned to their numbers and the nature of the organs they infest.

Many species of entozoa have been discovered in man, and most of them are peculiar in kind. Many are common, and, while some are widely extended, others are more or less restricted to certain localities. They are variable in their frequency, largely proportioned to the prevalence of habits which are favorable to their transmission, and which, though under control, are more or less disregarded. Some species are so rare in their occurrence that they seem to be accidental, and therefore of comparatively little interest to the physician.

In general, the frequency of occurrence of intestinal worms is proportioned to the extent of use of uncooked or insufficiently cooked meats, the drinking of unfiltered standing waters, uncleanly habits, and the intimacy of association with domestic animals. It therefore follows that important prophylactics against infection by parasites are properly-cooked food, the use of spring or freely-running water or filtered standing water, cleanly habits, and the avoidance of intimacy with domestic animals.

The Cestodes, or Tape-worms.

Tape-worms in the mature condition inhabit the intestines of vertebrate animals, and are usually conspicuous for their long, tape-like appearance and jointed character. In the juvenile or larval state they infest the various organs, except the interior of the intestinal canal, of both vertebrates and invertebrates, and in this condition are so diminutive and inconspicuous that until a comparatively recent period they for the most part remained unnoticed, and when known their relationship with the mature forms was not recognized.

The mature tape-worm, as ordinarily observed, is a long, soft, flat, white worm, which from its resemblance has received its familiar name. It has a small head, succeeded by a short, more slender neck gradually widening into the body, which is divided transversely into segments. These, which are usually called joints or links, and also named proglottides, are so many individuals, and finally become separated to hold an independent existence. The tape-worm clings to the mucous membrane of the intestine by its head, which is provided for the purpose with suckers, and in many cases also with circlets of hooks. The segments of the body are incessantly produced by gradual growth and successive division of the neck, and as they enlarge they become more distinct and develop within a bisexual generative apparatus for each. The worm has neither mouth nor intestine, but is nourished by imbibition from the surrounding liquid in which it lies constantly bathed. A pair of longitudinal vessels commences in the head and extends throughout the body, one on each side, and in some genera is joined by a transverse vessel at the fore and back part of every segment. The mature segments have no body-cavity, but are occupied with a complex bisexual generative apparatus, which is self-impregnating. Finally the uterus, usually much ramified, becomes especially conspicuous through distension with eggs, and the rest of the organs for the most part become atrophied. The ripe segments successively detach themselves from those in advance, often singly and not infrequently several linked together. In this condition, often in lively movement, they are discharged with the feces, and thus commonly render themselves obvious to their host. Subsequently they may continue to live a brief period externally in a non-parasitic condition. Ordinarily, in moist excrement, or in water or similar materials, they will remain alive for several days.

After the discharge of the tape-worm segments, together with the eggs which had been previously laid by the latter and those still contained within them, any or all may be swallowed by animals feeding in places where the infected excrement has been deposited. When the proglottides and eggs are taken into the stomach they are digested and the embryos or proscolices are liberated.

The embryo or proscolex of the tape-worm is a microscopic spherical or oval body, provided at one pole with three pairs of divergent spicules, by which it is enabled to penetrate the walls of the stomach or intestine of its host. From these positions the embryo migrates either directly or through the blood-vessels to some other organ, most frequently the liver or the muscles. Having reached its destination, it becomes fixed in position, and for a time remains comparatively quiescent, but undergoes further development. The embryo loses its spicules and is transformed into the larval form or scolex. In most species of tape-worms the scolex is simple or individual in character, and consists of a head like that of the parent or mature worm, with a neck ending in a capacious cyst, within which the head and neck are inverted. In this form the scolex is contained in a sac of connective tissue induced by the presence of the parasite. Such sacs, frequently observed imbedded in the flesh, liver, lungs, and other organs of animals, are familiarly known as measles. In this condition the scolices of certain tape-worms have long been known, but as their relationship was not recognized, they were viewed as distinct species of parasites and described as cysticerci. In other species of tape-worms the scolex is of compound character; that is to say, the embryo in its further development gives rise to the production of one or more groups of individuals in conjunction. The compound scolex thus forms a sac or a group of sacs, the basis of hydatid tumors. These occur of various sizes, even up to that of a child's head, and may occupy any organ of the body. They consist of a spherical sac or group of sacs, simple in character or containing others, ranging in size from that of a mustard-seed to that of a marble, or larger to that of a walnut, enclosed in an envelope of connective tissue induced by the presence of the parasite. The sacs are filled with liquid, and have, attached within or free and floating, or less frequently attached without, variable numbers of little white grains, which on examination with the microscope exhibit the same constitution as the simple scolex above described. As in the case of the cysticerci of measles, the scolices of hydatids have long been known, but as their relationship with the mature forms was unrecognized until lately, they were regarded as distinct parasites and described as echinococci and coenuri. Sometimes the compound scolex fails in development further than the production of the sacs, which then constitute the so-called acephalocysts.

Measles with their occupants, when retained in the muscles or other organs, ordinarily undergo no further development, but ultimately, after some months to a year or two, undergo degradation. The larva or scolex dies and atrophies; the measle degenerates, and often becomes the focus of calcareous deposit, shrinks to a little cicatrix, and may finally disappear. Of a more serious nature is the tape-worm embryo which produces the hydatid tumor. With the increase of this, proportioned to the production of sacs and scolices, it may become so large as greatly to interfere with the function of the organ it occupies, and according to the nature of this organ will be the gravity of the affection.

When, however, the flesh or other parts of animals affected with measles or hydatids containing active scolices are used as food in a raw or insufficiently cooked state, the meats are digested in the stomach and the scolices liberated to pursue their further development. Passing into the small intestine, the active scolex everts its head from its caudal sac, which atrophies and disappears, and the parasite attaches itself to the mucous membrane, and rapidly develops and grows into the conspicuous and familiar form of the adult tape-worm. The duration of life of the latter while maintaining its position in the intestine is uncertain, but under favorable circumstances it commonly continues for years, and thus, with the incessant production of ripe segments charged with eggs, it becomes a constant focus of infection.

Three species of tape-worm in the mature condition are common parasites of man, living in the small intestine. They are the Tænia saginata, Tænia solium, and Bothriocephalus latus.

TÆNIA SAGINATA.—SYNONYMS: Tænia mediocanellata; Beef tape-worm; Unarmed tape-worm; Fat tape-worm.

Larval condition: Cysticercus saginata; Beef measle-worm.

This, which is now regarded as the most common tape-worm of man, is named the beef tape-worm because it is derived from the beef used as food. In the mature condition it lives only in the small intestine of man, and in the juvenile condition it lives in the ox. Its frequency is proportioned to the prevalence of the custom of eating beef in a raw or insufficiently cooked state, conjoined with the careless habit of leaving human excrement in pastures where it is accessible to cattle.

The mature beef tape-worm is commonly observed as a soft, yellowish-white, thickish, band-like worm, ranging from six to twenty feet or more in length. The head, about the size of a yellow mustard-seed, is rounded quadrate and provided with four equidistant hemispherical suckers. Succeeding the head is a short, slightly narrower, flattened neck, which merges into the gradually widening and segmented body. The segments, at first narrow fore and aft and several times wider than the length, become successively larger, proportionately longer, more distinct, and quadrate in outline; and finally the length may exceed the breadth two or three times. A full-grown tape-worm may possess twelve hundred segments and more, and specimens are recorded as reaching a length of thirty feet. The larger segments measure from a quarter of an inch to an inch long and from three to four lines wide. The larger or riper segments exhibit on one border, irregularly alternating on the two sides, at or near the middle, a papilla in which is the external aperture of the genital apparatus. In the fully-ripe segments the uterus, distended with eggs, may be obscurely seen through the wall of the body, but is rendered more visible by drying the segments, moderately compressed, between two pieces of glass. It appears as a long, narrow, white or brownish median line or tube, giving off laterally numerous short, transverse, more or less branching tubes.

The worm in its usual position lies along the course of the intestine in loose coils, and exhibits lively movements, alternately shortening and elongating, expanding and contracting the head, and protruding and retracting the suckers. The ripe segments spontaneously detach themselves, and may be found scattered along the large intestine ready to be discharged with the excrement, or, as is sometimes the case, they may spontaneously creep from the anus. Rarely more than a single worm infests a person at the time. The species is of rapid growth. According to Perroncito, quoted by Cobbold, a mature worm was reared from a beef measle, swallowed by a student, in fifty-four days.

It is estimated that the number of eggs in the mature segments of the beef tape-worm amounts to about 35,000. As the full-grown worm may consist of 1200 segments, and there is reason to believe these are renewed several times annually, we learn that the whole number of eggs produced by a single individual is enormous. The ripe segments, attached to the parent or becoming spontaneously detached, lay their eggs in the intestine to be discharged with the feces. When more or less emptied they shrink and appear reduced in size, and in this condition are expelled or spontaneously creep from the anus. If the ripe segments are forcibly expelled and are alive, they will lay their eggs in the feces externally. The ripe eggs are brown, oval, about 0.03 mm. long, and have a thick shell, with an outer vertically striated envelope.

As previously intimated, the common source of the beef tape-worm in man is the use of raw or insufficiently cooked beef affected with measles. The ox becomes infested by swallowing the eggs, or, it may be, even the entire segment, of a tape-worm deposited with feces in the pastures of cattle. The measles usually occur in the muscles, including the heart, though they have also been noticed in the liver and lungs. They appear, in beef, as oval, whitish bodies from the size of a mustard-seed to that of a pea. They consist of a sac of connective tissue containing the larval tape-worm or cysticercus. Measles under ordinary circumstances are seldom noticed in beef, and when they occur are commonly few in number.

According to the latest authorities—Leuckart, Cobbold, Stein, and others—the beef tape-worm is the most common of the cestodes which infest man. Until within about thirty years it was generally not distinguished from the pork tape-worm, and this was accordingly regarded as the most common human species. Since the writer distinctly recognized the beef tape-worm within the last twenty years, all the specimens of Tæniæ, from people of Philadelphia and its vicinity, that have been submitted to him for examination—perhaps in all about fifty—have appeared to belong solely to Tænia saginata. The prevalence of this species with us is no doubt due to the common custom of eating underdone or too rare beef, while the pork tape-worm is comparatively rare, as with us pork is only used in a well-cooked condition.

TÆNIA SOLIUM.—SYNONYMS: The Pork tape-worm; Solitary tape-worm; Armed tape-worm.

Larval condition: Cysticercus cellulosæ; Pork measle-worm.

Until a recent period this species was generally regarded as the most common tape-worm of man—a view which in great measure was due to the circumstance that the beef tape-worm was not distinguished from it. It was called the solitary tape-worm, still expressed by the specific name, from the impression that it rarely occurred otherwise than single at a time in a person. This has also proved to be incorrect, likewise due to the two kinds of tape-worms having been confounded together; for while the beef tape-worm most commonly occurs solitary, the pork tape-worm not unfrequently occurs with several together.

The species is now appropriately named the pork tape-worm, as indicating its common source—pork used as food. The frequency of the parasite is proportioned to the prevalence of the custom of using pork in a raw or imperfectly cooked state, conjoined with that of depositing excrement where it may be accessible to hogs. In the mature condition the pork tape-worm is peculiar to man and lives in the small intestine, but in the larval condition, though especially infesting the hog, it also occasionally infests man, and lives in any organs of the body, but mostly the muscles, liver, and lungs.

The mature pork tape-worm, as commonly seen, is a soft white, thin, band-like worm, from five to ten feet long and about four lines where widest. The head is spheroid, about the size of that of an ordinary pin, and smaller than that of the beef tape-worm. It is furnished with four hemispherical cup-like suckers, and the summit forms a blunt papilla armed with a double circle of twenty-five or twenty-six hooks. The neck is narrow, thread-like, about an inch long, and merges into the segmented body, which gradually widens to the extent mentioned. The segments, at first much wider than long, as they successively enlarge also become more distinct and proportionately longer, so that the more posterior ripe ones are as long as they are wide, and often longer, though not to the same degree as in the beef tape-worm. The genital papilla, with its external aperture, is marginal as in the latter. The fully-developed uterus is quite distinctive in character from that of the beef tape-worm. The median tube is coarser, and the lateral branches are likewise coarser, much fewer—half the number or fewer—less branched, and less crowded. The ripe and often spontaneously detached segments are commonly longer than broad, more or less elliptical in outline, with truncated ends, and usually measure about half an inch in length by about a third in breadth. The ripe eggs resemble those of the beef tape-worm, but are usually spheroid in shape.

The common source of the pork tape-worm is pork affected with measles eaten in the raw or insufficiently cooked state. The hog becomes affected with measles when it has access to human excrement containing eggs and ripe segments of the tape-worm, which it eats with avidity. The eggs, with their already developed embryos, when swallowed, undergo the same series of transformations and course as those indicated in the account of the beef tape-worm. Pork affected with measles is much more common than beef affected in the same way, and is frequently a subject of ordinary observation. From the difference in habit of the hog and ox this is what might have been suspected; and the fact that the beef tape-worm is more common than the pork tape-worm is to be explained from the circumstance that fresh beef is in more general use than pork, and is usually employed less thoroughly cooked.

The pork measles are commonly seen as round or oval, hard, whitish bodies, from the size of a hempseed to that of a pea, imbedded in the connective tissue of the muscles or flesh. The measle consists of a sac of connective tissue enclosing the scolex or larval tape-worm, which resembles that of the beef tape-worm, but differs especially in the possession of a double circlet of hooks to the head, as in the adult worm. The scolex has long been known, and was regarded as a distinct parasite, with the name of Cysticercus cellulosæ. When fresh pork measles are swallowed by man they are digested in the stomach, and the cysticercus or scolex is released and passes into the small intestine. Here, attaching itself to the mucous membrane by means of its suckers and crown of hooks, it rapidly develops and grows into the adult tape-worm. In this condition it lies in loose folds along the intestine, to which it clings so tenaciously that commonly the neck gives way when the greater part of the worm is forcibly detached by the use of medicines. Fragments, consisting of the more mature segments, frequently appear detached from the posterior part of the worm, and the fully-ripe segments may be seen scattered singly in the course of the large intestine. The isolated segments are thinner and more translucent than those of the beef tape-worm, and in this condition are discharged with the feces, but may also spontaneously creep from the anus, though seldom as compared with the other species.

Experiments repeatedly made by swallowing pork measles prove that the mature tape-worm may be developed in the course of three months. The length of life attained by it under favorable circumstances is uncertain, but it probably continues a dozen years or more.

The scolex of the pork tape-worm, or the cysticercus, so common in the hog, is also less frequently a parasite of man, and in this condition is a more potent agent of danger than in its ordinary or mature state. The infection is due to the introduction of eggs or mature segments of the tape-worm into the stomach—a circumstance which may readily occur through handling these objects and transferring them to the mouth, or more rarely perhaps by their transference from the intestine into the stomach through vomiting.

In the measle form the parasite may occur in any organ of the body, but is mostly found in the muscles and subcutaneous tissue. Its pathological significance depends on its number and position. Located in the nerve-centres, it may occasion the most serious consequences. Usually it occurs in small numbers and gives rise to no obvious inconvenience, and is only accidentally detected in dissection after death. It appears to maintain its vitality for some years, but finally dies, and undergoes degradation. Only when it can be detected in such position as the interior of the eye or beneath the conjunctiva can the patient be relieved by surgical aid. Elsewhere, even if its presence is suspected, it is ordinarily beyond the reach of medical treatment. The writer a few years since, in dissecting the body of a colored man to illustrate his lectures on the muscles, found two living measles, of which one was in the diaphragm and the other in the transversalis muscle of the abdomen, but none were detected elsewhere. The parasite unquestionably gave no inconvenience to its host during life.

Other species of Tænia which have been observed as parasitic in the human intestine are mostly of rare occurrence.

TÆNIA CUCUMERINA, the common tape-worm of the dog, and TÆNIA ELLIPTICA, the common tape-worm of the cat, are very much alike in appearance, and are regarded by many authorities as the same species. They occur frequently in considerable numbers in these animals, living in the small intestine. They have also been occasionally found in man, especially children.

It is a comparatively delicate worm, chain-like in appearance, ranging from four inches to a foot in length. The head is provided with four suckers and a prominent rostellum armed with about sixty hooks. The neck and anterior part of the body are thread-like. The mature segments are elliptical in outline or like a melon-seed, whence the name. There is a double set of sexual organs, and a genital orifice occupies the middle of both lateral margins of the segments. The ripe segments become readily detached and creep actively in the intestine, and are either expelled with the feces or they spontaneously creep from the anus. The eggs are comparatively few and measure 0.05 mm.

Late researches appear to show that the eggs adhering to the hair about the anus or elsewhere are eaten by lice of the same animals, and within these insects undergo further development. The dog and cat, subsequently swallowing the lice, infect themselves with the mature worms. Thus also persons, especially children, from too great familiarity with these animals, directly or through their food, may likewise become infected.

TÆNIA NANA, the Dwarf tape-worm, has been observed but once. It was discovered by Bilharz, in Egypt, in a boy who died of meningitis. It is a little worm, about half an inch in length, and occurred in large numbers in the duodenum.

TÆNIA TENELLA.—This is another small species, which has been but once observed. It is described by Cobbold, who suspects it to be derived from measles of the sheep.

TÆNIA FLAVOPUNCTATA is also a small species, from eight to ten inches long, with ripe joints about one millimeter long and from one and a half to two millimeters broad. It is described by Weinland, and has also been but once observed. A half-dozen specimens were discharged from a healthy child, of nineteen months, in Boston, Mass.

Since the above was written the author has had the opportunity of examining some little tape-worms which he suspects to be of the same kind as the former. They occurred in the practice of T. V. Crandall in Philadelphia, and were expelled from a child of three years of age after the use of santonin. About a dozen fragments appear to have pertained to three worms, from twelve to fifteen inches in length. The head in all was lost. The anterior part of the body is thread-like, the posterior part about two and a quarter millimeters wide. The width of the joints is more than twice the length. The ripe joints are pale brown, and are remarkable for the comparative simplicity of the uterus, which is distended with brown eggs. A peculiarity of the worm is the repeated but irregular alternation of fertile with sterile joints.¹

¹ Amer. Journ. of Medical Sciences, 1884, p. 110.

The species is probably more common than might be supposed, and from its small size, and perhaps harmless character, has generally escaped notice.

TÆNIA MADAGASCARIENSIS.—This species, described by Davaine, is imperfectly known. Fragments of the worm have been twice observed in the Comoro Islands.

BOTHRIOCEPHALUS LATUS.—SYNONYMS: Dibothrium latum; Tænia lata; Broad tape-worm.

This tape-worm, of another genus than the preceding, is a common parasite of man in certain localities of Europe, but has not been found as an indigenous product elsewhere. It occurs especially in Sweden and Russia, East Prussia, Poland, and West Switzerland. In the latter country it prevails to such an extent that it is reported that about one-fourth of the inhabitants of Geneva are thus infested. Among the tape-worms submitted to the writer from time to time for identification a few years ago was a large specimen of Bothriocephalus latus, but it proved to have been derived from a Swede who had arrived in this country only a few months previously.

There are many species of Bothriocephalus, which in the adult condition mainly live in fishes. The genus is distinguished from Tænia by many points, chiefly in the form and construction of the head, the form of the joints and uterus, and the position of the genital aperture, which is situated centrally on one of the broad surfaces instead of the lateral margin.

The broad tape-worm is the largest of the tape-worms infesting man, a full-grown specimen reaching to twenty-five feet in length with a breadth of three-fourths of an inch, and consisting of upward of four thousand segments. It is a soft, grayish, flat, band-like worm, with head, neck, and segmented body holding the same proportions as in the other tape-worms. The head is elongated, clavate, and is provided with a long, narrow, elliptical sucker on each side. The narrower neck is short and merges into the segmented body, which gradually widens to half an inch or more. As the segments successively enlarge, they increase proportionately to a greater extent in breadth, so that their width for the most part measures from two to four times their length. A few toward the end of the series become narrower and longer than those in advance. In the ripe segments the uterus, distended with brownish eggs, forms a central rosette-like group of pouches. The genital aperture is central in the broad surface of the segments, and is always on the same or ventral side.

The broad tape-worm inhabits the small intestine, and is usually found single, but occasionally several together, and sometimes also in association with one or both the other common tape-worms. The species is also reported to be not infrequent in the dog.

Ripe portions of the broad tape-worm become detached in fragments of variable length, to be discharged with the feces. The partially-emptied appearance of the uteri in these fragments indicates the laying of the eggs previous to the expulsion of the latter. The eggs are oval, of a light-brown color, and measure about 0.07 mm. long. The shell at one pole is furnished with an operculum or lid for the escape of the embryo. This is developed subsequently to the discharge of the eggs from the intestine. If the eggs are placed in water, in the course of some months the embryos are developed and escape from the shell. The embryo is a round or oval body furnished with three pairs of spicules, as in that of the Tæniæ, but differs in possessing a ciliated envelope, by means of which it freely swims about in the water. After some days the embryo discards its envelope and creeps about in an amoeboid manner. Further than this, until recently, the fate of the embryo was unknown. Braun of St. Petersburg, after determining the presence of scolices of Bothriocephalus in the muscles, liver, and organs of generation of the pike, trout, and eel-pout, by feeding these to cats and dogs succeeded in rearing worms which differed in no respect, except in being smaller, from the Bothriocephalus latus of man. Such being the case, it becomes evident that man may ordinarily become infested with the parasite by eating raw or insufficiently cooked fishes of the kind mentioned.

BOTHRIOCEPHALUS CORDATUS, described by Leuckart as a common species infesting the dog in Greenland, has been reported as having once been found in a woman. Böttger regards it as not distinct from Bothriocephalus latus.

BOTHRIOCEPHALUS CRISTATUS.—This species, but once observed, is described by Davaine. It was passed by a child in Paris, and the worm was upward of nine feet in length.

SYMPTOMS OF TAPE-WORMS.—Whichever may be the species of tape-worm infesting the human intestine, the symptoms to which it gives rise are mainly of the same character, modified of course in degree by the size and number of the parasites and the susceptibilities of the patient. Clinging by means of the head to the mucous membrane of the intestine, and involved among the valvulæ conniventes and villi, the worm may extend in loose folds along the greater part of the course of the intestine or lie coiled in an elongate mass. Besides being rendered evident from time to time by the discharge of segments or fragments, the beef tape-worm especially sometimes introduces itself to the notice of its host through the segments creeping from the anus. Sometimes segments of tape-worms are vomited, especially in women; and the exhibition in this way, especially of the pork tape-worm, is to be deplored, for should segments be retained in the stomach the patient becomes further liable to be affected with measles or cysticerci.

Some persons continue infested with a tape-worm a long time without suspecting its existence and with little or no inconvenience, and perhaps first become aware of its presence by the accidental discovery of segments discharged from the bowels. Usually, however, the parasite creates more or less disturbance, and not unfrequently occasions great discomfort. The symptoms are both local and of a general nature. Itching at the extremities of the alimentary canal and various dyspeptic symptoms are common; uncomfortable sensations in the abdomen, uneasiness, fulness or emptiness, feeling of movement attributed to the worm, and colicky pains; disordered appetite, sometimes deficient, oftener craving; paleness, discoloration around the eyes, furred tongue, fetid breath, and sometimes emaciation; fulness of the forehead, dull headache, buzzing in the ears, twitching of the face, and dizziness; often uncomfortable feelings in the abdomen increased by fasting, which are temporarily relieved by taking a full meal. Certain kinds of food also at times appear to produce greater uneasiness, apparently due to more than usual disturbance of the parasite. Symptoms of a more grave character are sensations of fainting, chorea, and epileptic fits. Others of a chlorotic and hysterical character are not unfrequent, especially in women, who also may suffer more or less from uterine disorder.

All the ordinary symptoms are quickly relieved by the expulsion of the tape-worm—permanently if it is entirely removed, but temporarily, as is frequently the case, when only the greater bulk of the parasite is discharged and the head continues to remain securely attached to the intestine and ready to renew its many-segmented body. The tape-worms are capable of a wonderful amount of extension from traction without detachment; and from the delicacy of the neck and the anterior part of the body, and the action of medicine on the peristaltic motion of the intestine, the posterior part of the worm, including its great bulk, is most apt to be torn away and discharged, while the head remains. So long as this is the case, and the worm has not been poisoned or killed, the anterior portion grows, and thus the parasite is renewed and accompanied by a return of all the former symptoms. Under the appropriate treatment the evacuations of the patient should be carefully inspected, so as to satisfy both physician and patient that the parasite has been completely expelled. To properly examine the evacuations, they should be repeatedly drenched with clear water, and the sediment, after the settling of the washings, must be inspected. It is only when the physician has seen the head of the parasite that he can reasonably ensure his patient a permanent cure.

TREATMENT.—To get rid of tape-worms many remedies have been employed, though comparatively few retain a reputation for positive success. Some act by powerfully operating on both bowels and worms, producing the detachment and discharge of the latter without killing them, as is often indicated in the lively movements they exhibit after their expulsion. Others poison and kill the worms, and also cause their detachment and expulsion from the bowel.

Before the administration of the appropriate medicine for tape-worms, with the object of rendering it more effective it is advisable to bring the alimentary canal into a condition which will render the parasites most vulnerable. For this purpose fasting is to be recommended for several days previously, and when food is used it should be in moderate quantity, and of such a character as to leave little residue to accumulate in the intestine. Wheat bread, the ordinary meats, milk and coffee, are best, while the usual vegetables should be avoided.

One of the most effective remedies is the oil of turpentine in the dose of one or two fluidounces, made into an emulsion with white of egg and sugar; children require about half the quantity. The large dose is less apt to produce the usual objectionable effects of that medicine than small ones. The only inconvenience caused by it is the heat of the stomach, some febrile excitement, and fulness of the head or headache lasting for one or two days. The effects are more apt to occur when the medicine does not act as a cathartic. The oil usually operates quickly, killing the worm and producing its discharge. If it does not act in the course of two or three hours, a full dose of castor oil may be given, and, if necessary to aid the action of this, enemata may be employed. To ensure the purgative action of the oil of turpentine it may be advantageously associated with the castor oil, of each a fluidounce made into an emulsion.

Another and effective remedy is the root of the male fern, Aspidium filix-mas, used in decoction or electuary. Stein of Frankfort recommends the ethereal extract as the best preparation, and prescribes it in doses of from seven to ten grammes, enclosed in half the number of gelatin capsules and administered at short intervals within half an hour. It should be taken in the morning fasting, after taking a cup of coffee, swallowing the capsules with the aid of a second cup. Half an hour after the capsules are taken a mixture of castor oil, brandy, and ginger syrup, of each fifteen grammes, should be administered. The treatment has proved all that could be desired, and the worm, including the head, is discharged altogether, rolled into a ball.

The bark of the pomegranate-root, Punica granatum, is also a powerful and efficient remedy, but often proves very disagreeable from its producing violent pains in the abdomen, with nausea and vomiting. It also generally purges, occasioning the discharge of the worm. Küchenmeister prefers it to any other medicine, given in the form of decoction prepared by macerating three ounces of the fresh bark in twelve fluidounces of water for twelve hours, and concentrating the infusion by gentle heat to one-half. He recommends it to be taken after fasting a day and the administration at night of two fluidounces of castor oil. It is to be given in three or four doses within an hour. Should the medicine not purge, it should be followed by another dose of castor oil.

Recently, Feraud has recommended the tannate of pelletierin, the alkaloid of which is derived from the pomegranate-root, as the most powerful of remedies for tape-worm, the dose for an adult being one-half to three-fourths of a grain. The patient should fast a day on bread and milk, and the following morning, before rising, take an infusion of one-third of an ounce of senna. This should be followed an hour later by half the medicine diffused in a little water, and the patient should remain quiet in bed to avoid nausea and vomiting. Half an hour later the rest of the medicine is to be given, followed in another half hour by a dose of castor oil. Should there be no stool after an hour, purgative enemata may be used. In one case twelve beef tape-worms were discharged together measuring, collectively, fifty meters.

Kousso, the flower of Brayera anthelmintica, an Abyssinian herb, has been of late much employed as a remedy for tape-worms, but with many physicians of experience it has lost favor. Heller speaks of it highly, and recommends it to be taken in the morning, an hour after the patient has taken coffee. The dose is from half an ounce to an ounce, and is conveniently taken in compressed balls or disks, coated with gelatin, and swallowed at intervals in the course of an hour, aided by mouthfuls of coffee. Any disposition to vomit should be repressed, which is rendered easier by taking small mouthfuls of strong coffee or pieces of ice.

Koussin, an alcoholic preparation of kousso, is also efficient, and has the advantage over the latter that it does not occasion nausea. It has been used in the medical clinic of Munich in the dose of 30 grains, and it has been a very rare occurrence that the result was not all that could be desired.

The seeds of the common pumpkin, Cucurbita pepo, are extolled by many physicians as a remedy for tape-worms; and the writer has twice had the opportunity of observing large specimens of the beef tape-worm which were expelled after the administration of this medicine. The dose is an ounce of the seeds bruised into a paste and made into an emulsion. It should be taken in the morning, fasting, and followed in an hour or two with a full dose of castor oil.

Santonin, a principle derived from santonica, Artemisia maritima, is reported as a remedy for tape-worms, but its efficacy has also been denied. The dose is from two to four grains for an adult, and from one-quarter to one-half a grain for children over two years. It is best administered in lozenges prepared with sugar and tragacanth.

The quinia sulphate has also been recommended as an effectual remedy both in tape- and seat-worms.

As regards the prophylaxis of tape-worms, there are some important points to which we direct attention.

The evacuations of patients containing tape-worms, their segments and eggs, should not be carelessly thrown away, at least in places accessible to animals which may become infected. They should be treated with boiling water, the heat of which is sufficient to kill all animal parasites. The handling of living tape-worms and segments should be avoided, as eggs which may adhere to the hands, if transferred to the mouth and swallowed, will produce infection.

Meats visibly infested with measles are not fit and should not be used as food. Raw meat should altogether be discarded as food, both for the sick and well, and all meats should be thoroughly cooked. As a rule, meat should not be used so long as it appears red or on cutting emits a bloody liquid. A large piece of meat requires long boiling or roasting for sufficient heat to penetrate to the interior to destroy any parasites that may be present. Even salted meats and hams should be cooked to ensure against parasitic infection. It is important also to avoid food prepared by uncleanly persons who may be infested with tape-worms.

As regards our domestic animals, which are the common source of the infection of man with tape-worms, they should also be protected from infection as far as possible. This is to be done by preventing them from having access to human excrement. As Heller remarks, with this object the barbarous custom of defecating in every place promiscuously should be put down with a high hand.²

² Several years since a physician of Texas sent to the writer a piece of pork, making inquiry as to its condition, and stating that all the pigs of his vicinity were diseased and their flesh similarly affected. It contained a number of measles or larval tape-worms. On giving the information and the probable cause of the affection of the pigs, the doctor reported in return that there was not a privy in his village. Until our people are more careful with the raising of pigs, European governments will have reason for prohibiting the importation of our pork.

TÆNIA ECHINOCOCCUS.—SYNONYM: Hydatid tape-worm.

Larval condition: Echinococcus; E. hominis; E. veterinorum; E. granulosis; E. scolicipariens; E. altricipariens; E. hydatidosus; E. multilocularis; E. cyst; Hydatid; Hydatid cyst; Acephalocyst.

This tape-worm, in its mature state the most insignificant looking of its kind, though not strictly an intestinal worm of man, in the juvenile condition is one of his most dangerous parasites, as being the source of hydatid tumors. The adult tape-worm lives in the small intestine of the dog and wolf, in some localities often existing in these animals in thousands together. From its diminutive size it may be readily overlooked, concealed or obscured by the villi among which it is suspended to the mucous membrane. It is about a fourth of an inch in length, and consists of but four segments, of which the last alone exhibits the ripe condition. The head resembles in construction that of the pork tape-worm, being provided with four suckers and a prominent crown, with from thirty to fifty hooks arranged in a double circle. The terminal ripe segment exceeds in size all the preceding together, and before it separates from the series another is ready to take its place. The ripe eggs contain the usual six-spined embryo as in other tape-worms.

The mature worm is remarkable for the comparative shortness of its life, which, according to Siebold, is about seven weeks. Apparently to compensate for the small number of its segments, the larval form is endowed with the power of multiplying itself to a wonderful degree.

It is only in the larval condition that the hydatid tape-worm infests man, and in this state also it infests the ape, the ox and sheep and other ruminants, also the horse, hog, and indeed many other animals of the same class.

If the eggs of the tape-worm are swallowed, which may readily happen by too free intimacy or association with infested dogs, the liberated embryos obtain access to the intestine. Penetrating the mucous membrane, the embryos thence may migrate to any part of the body. From the comparative frequency of hydatid tumors in the liver we may suspect they mostly enter the portal venous system and take the course of the blood-current. It is, however, probable that they migrate directly to their destination, for hydatid tumors are also frequently seated in the neighboring organs and the abdominal walls. The embryo tape-worm, once fixed in position, becomes the starting-point of a hydatid tumor.

When dogs are fed on the liver, or other parts affected with hydatid tumors, from the sheep or other animals, the scolices are liberated, and, passing into the small intestine, are there developed into the mature tape-worms.

Hydatid tumors occur in any of the organs of the body, but are more frequent in the liver than in all others together. They are common in the lungs, kidneys, spleen, omentum, and subperitoneal tissue of the abdominal walls. They are less common in the heart, brain, spinal canal, the pelvic viscera, and the bones. Mostly but a single tumor is found in the same person, but occasionally several occur together in the same or in different organs.

There are several varieties of the hydatid tumor. In man the more common form consists of a cyst or a group of cysts enclosed in a connective-tissue envelope induced by the presence of the parasite. The simple cyst is produced through the transformation of the echinococcus embryo, and the group of cysts is derived from the former by proliferation; and hence the first has been called the parent cyst, and the others the daughter cysts. These also in the same manner may produce a third series, called granddaughter cysts. The parent cyst, at first spherical, becomes modified in shape according to the space it occupies and the resistance to which it is subjected, thus assuming an oval, lobulated, or other form. It may increase in size to that of a cocoanut or larger, and may remain simple, but usually is compounded by proliferation in the production of daughter cysts. These may be few or many up to hundreds, and range from a minute size up to that of a walnut, and are spherical or modified in shape by mutual pressure or other cause. The cysts are filled with a clear watery liquid of saline taste, but without albumen.

The hydatid cysts are usually composed of an outer thick, translucent, homogeneous, laminated, glistening, highly elastic membrane, the ectocyst, and an inner thin, granular, and cellular layer, the endocyst. From the endocyst originate minute buds, which become the brood-capsules of the larval worms or scolices. These form little groups of a few to a dozen individuals suspended within the brood-capsules, but capable of eversion from them. The individual scolices, which appear to the naked eye as mere white points, have the form and construction of the head-segment of the mature Tænia echinococcus. After death or by violence they become easily detached, and then float free in the liquid containing them. In some cases the echinococcus cysts develop no scolices, in which condition they constitute acephalocysts. Occasionally the echinococcus embryo undergoes imperfect development, constituting the multilocular hydatid tumor, rarely found elsewhere than in the liver.

Echinococcal tumors, especially those which have many daughter cysts, when accessible are remarkable for exhibiting a tremulous movement when grasped by the hand and quickly tapped with the finger.

Infection through the embryonic form of the Tænia echinococcus, as the source of hydatid tumors, is productive of the most disastrous consequences, and has ended in the destruction of many lives both of men and domestic animals. The parasite is not directly productive of suffering, but its effects and dangers are proportioned to the size of the tumor it occasions and the character and importance to life of the organ in which the latter is situated. With the increase of the hydatid tumor, usually of very slow growth, it encroaches upon the surrounding parts, and if these are not displaced they become disorganized and atrophied.

The liability and frequency of infection with the hydatid disease appear to be proportioned to the prevalence of intimate association with the dog. In Iceland, in which it is said every peasant owns half a dozen dogs, which share his dwelling with him, it is also reported that one-sixth of all the deaths are due to the hydatid parasite.

Ordinarily, the hydatid disease is beyond the reach of medical treatment. The mercurials and potassium iodide have been recommended, but the results are very doubtful. Apparently as an indication how little hydatid parasites may be influenced by medicine, the following incident will show: The writer once received for dissection the body of an English sailor which had been injected with zinc chloride for preservation. In the abdominal wall in the right iliac region there was a hydatid tumor the size of a fist. On examination of the tumor it was found full of daughter cysts, and these contained living scolices, though the man had been dead several days and the tissues were bleached by the zinc solution.

Favorable results in the treatment of hydatid tumors are only to be expected through surgical means when they are accessible.

As a prophylactic measure against infection the avoidance of too intimate association with dogs is especially to be recommended.

In concluding the chapter on Tænia echinococcus, as a prophylactic against this and other parasites Cobbold gives the advice that "all entozoa which are not preserved for scientific investigation or experiment should be destroyed by fire when practicable, and under no circumstances whatever should they be thrown aside as harmless refuse."

TÆNIA ACANTHOTRIAS.

Larval condition: Cysticercus acanthotrias.

This species has been but once observed, and only in the larval condition or that of the scolex, which was first described by Weinland. About a dozen specimens were found by Jefferies Wyman of Boston in the body of a woman of Virginia who died of phthisis. They were situated in the connective tissue beneath the skin and in the muscles, except one, which was attached to the dura mater. The scolex is distinguishable from that of the other human tape-worms in possessing a triple circle of hooks. The mature form of the worm remains unknown.

The Trematodes, or Fluke-worms.

The trematodes or fluke-worms, though allied to the tape-worms, differ in many important characters. In the mature condition, like the latter, they are solid worms or are devoid of a body cavity or coelum, and are with rare exceptions hermaphroditic. They are, however, never compound, but simple or consist of single individuals, and are provided with a mouth and alimentary canal, but this is closed or is without an anal aperture. They have a water vascular system, communicating with the exterior by a pore at the posterior extremity of the body. They are commonly of flat, elliptical shape, with a sucker-like mouth at the fore end, and with a second sucker situated ventrally near the middle.

The fluke-worms are remarkable for their successive transformations and course of life, and, like the tape-worms, they pass the different stages of their existence in different animals. A number of species have been described as infesting man, but most of them are, fortunately, of rare occurrence.

DISTOMUM HEPATICUM.—SYNONYMS: Fasciola hepatica; Liver-fluke.

This species, the common liver-fluke, occasionally occurs in the human body, but is especially frequent in the sheep and other ruminating animals, as the ox, goat, and deer, and it likewise occurs in the horse, hog, and some other animals. It usually inhabits the liver, occupying the bile-ducts, but is also sometimes found in the portal and other veins and in the intestine, and more rarely in abscesses beneath the skin. It is the cause of the affection in sheep called rot, of which many thousands die annually.

The liver-fluke is a flat, tongue-shaped, brownish worm about an inch long and about half as wide. It is invested with minute scale-like spines. The head end is somewhat prolonged, and terminates in a small oral sucker, a short distance behind which is a small ventral sucker. The intestine is forked and much branched. The genital aperture is situated between the oral and ventral suckers. The commonly yellowish eggs are numerous and large, oval, and measure about 0.135 mm. long.

The common liver-fluke frequently occurs in large numbers, even hundreds, in the liver of the sheep, obstructing the bile-ducts and occasioning more or less destruction of the organ. The eggs pass off with the bile into the intestine, and are discharged with the excrement. In water the eggs are hatched, and deliver a ciliated and freely-swimming embryo. This in favorable positions, such as marshy pastures, obtains access to small fresh-water snails and penetrates to the interior of their body. Here the embryo sheds its ciliated integument and is transformed into a sporocyst. This is an elliptical pouch containing reproductive bodies, which become developed into individuals of more elongated form than the sporocyst, provided with a mouth and stomach, and named redias, or nurses. The nurse penetrates to the liver of the snail, and there develops within itself new forms called cercarias, which resemble the parent fluke-worm, but are provided with a long, powerful tail and have no apparent generative apparatus. The cercaria escapes through an aperture of the nurse, and makes its way out of the snail into the water, where it swims about actively by means of the tail, much in the manner of a tadpole. The cercaria after a time fixes itself to a submerged plant, becomes encysted, shakes off its tail, and remains in a quiescent state. If in this condition, in the feeding of sheep or other animals, the tailless cercaria or incipient fluke-worm is transferred to the stomach, it makes its way to the liver, and there grows and is developed into the sexually mature worm.

Recently it has been ascertained both in England and Germany that the juvenile state of the fluke-worm is passed especially in the little fresh-water snail Lymneus truncatulus. As, however, the common liver-fluke occurs in America, while the last-named species of Lymneus does not, it is rendered probable that the juvenile condition of the parasite also occurs in other species of snails. Incidentally, the writer may here mention that he has found certain of our smallest fresh-water snails, such as Planorbis parvus, frequenting meadows in the vicinity of our rivers and creeks, swarming with nurses of several different species of fluke-worms.

Notwithstanding the frequency of the common liver-fluke in the sheep and other domestic animals, its occurrence has been rare in man, and in all the cases reported it has been few in number, either single or from two to half a dozen. In man it has been found to occupy the bile-ducts, the portal vein, and abscesses beneath the skin.

DISTOMUM LANCEOLATUM.—SYNONYM: Smaller Liver-fluke.

This species, much smaller than the preceding, is of lanceolate form, acute behind, smooth, and about a third of an inch long. Its suckers are moderately large, and the bifurcate intestine is unbranched. It infests the liver of the sheep and ox and some other animals, and not unfrequently is found in association with the former species. It usually does not occur in such great numbers together as in the latter; from which and other circumstances, as the smaller size and smooth investment, it does not produce the same serious results. Its continuous history remains unknown, though it is probable that its course is similar to that of the common liver-fluke. Several cases are reported of its occurrence as a parasite in man.

DISTOMUM SINENSE.—Under this head Cobbold has recently described a species somewhat larger than the D. lanceolatum. It occurs in the liver of Chinese.

DISTOMUM CONJUNCTUM.—Another species described by Cobbold under this name, originally found in the liver of an American fox, has also been detected in man. The worm is about one-fourth of an inch long.

SYMPTOMS.—Cases of fluke-worms in the human liver have occurred so rarely that we are not prepared to indicate with certainty what may be the nature of the peculiar symptoms. If the parasites were numerous, they would give rise to more or less obstruction of the bile-ducts, with accumulation of bile, accompanied with jaundice and other symptoms usually attendant on functional disturbance of the liver. As in sheep, they would occasion dilatation of the bile-ducts, catarrhal inflammation, incrustation with biliary matters, hyperplasia of the surrounding tissues, and more or less disorganization and atrophy of the secretory structure.

TREATMENT.—As regards the treatment, we can say almost nothing. In the destructive disease of rot in sheep there are no known means to expel the parasites from the liver. If present in man, as they occur but few in number, we may hope for their spontaneous expulsion in due time without leaving any serious result. As a means of prophylaxis persons should carefully avoid salads prepared from subaquatic vegetables, like cress, which may harbor little fresh-water snails.

DISTOMUM HETEROPHYES.—This is a small species, about half a line long, with the fore part of the body covered with minute spines, and having a large, nearly central, ventral disk. It has been but once observed, and was reported by Bilharz, in Cairo, as having been found, in the post-mortem examination of a boy, in the small intestine, in which it existed in hundreds.

DISTOMUM CRASSUM.—This is the largest of the fluke-worms infesting man, and measures from one to three inches in length. It is elliptical, comparatively thick, and smooth. The two suckers have nearly the same relative size and position as in the D. hepaticum. It inhabits the duodenum, and has been observed a number of times infesting inhabitants of China and India.

DISTOMUM RINGERI.—A species by this name, about half an inch long, has recently been described by Cobbold as infesting the lungs of people in Formosa and China.

DISTOMUM OPHTHALMOBIUM.—A minute species, described under this name, has been detected several times in the human eye.

BILHARZIA HÆMATOBIA.—SYNONYM: Distomum hæmatobium.

As a human parasite this is the most important of the fluke-worms, being the most common and dangerous. It is apparently restricted to Africa and Arabia, and is especially frequent in Egypt, Abyssinia, the Cape of Good Hope, and Natal. So far as known, it is peculiar to man and monkeys, and inhabits the veins, especially those of the portal system, and it lives on the blood.

The blood fluke-worm is remarkable among its kind in having the sexes distinct. The female is slender, cylindrical, and tapering toward the ends, looking more like an ordinary thread-worm than a fluke-worm, and is about three-fourths of an inch long. The male is about half an inch long, but wider than the female, which it partially embraces at maturity by doubling upon it laterally.

This parasite, of the same essential nature as the more ordinary fluke-worms, is most probably introduced in the juvenile condition into the stomach by drinking unfiltered standing waters, and perhaps also by eating vegetables which grow in wet places and upon which the young fluke-worms may be encysted. From the stomach the worms gain access to the portal venous system, within which they undergo development to sexual maturity. The worms, proportioned to their number, occasion more or less sudden and dangerous hæmaturia. According to Bilharz, who first discovered the parasite, it also induces inflammation of the ureters, bladder, and rectum, accompanied with ulceration and incrustations and concretions in the same, due to the abundant deposit of eggs in the mucous membrane. The symptoms in the hæmaturia are obvious; all treatment fails, but the prophylaxis is evident.

AMPHISTOMUM HOMINIS.—The genus Amphistomum is distinguished from Distomum in having the ventral disk placed at the posterior extremity of the body.

A species has been recently described by Cobbold under the above name, and is reported as having been observed several times in natives of India. It is a red worm, about the fourth of an inch long, and inhabits the cæcum and ascending colon, in which it was found in hundreds together. The mucous membrane exhibited venous congestion and was marked with numerous red spots resembling leech-bites, produced by the parasites. One of the patients died of cholera.

We have too little information as to the symptoms induced by this parasite, and of its treatment, to say anything. It is probable that calomel, turpentine, and castor oil would be appropriate remedies.

Several other fluke-worms which have been reported as having been found in the human body are generally viewed with doubt as to their genuineness. Such are the Hexathyridium pinguicola, from a tumor of the ovary; the H. venarum, said to have been found in the blood and in the sputum of hæmoptysis; and the Tetrastomum renale, said to have been found in the urine.

The Acanthocephali, or Thorn-head Worms.

The thorn-head worms in the mature condition are comparatively robust cylindrical worms, with a body-cavity or coelum, but devoid of mouth and alimentary canal. They are provided with a protrusile and retractile proboscis-like head armed with circular rows of recurved hooks, by which they firmly cling to the wall of the intestine of their host. The sexes are distinct. There are many species, which mostly in the mature state live in fishes. In the juvenile or larval condition they live in other animals, mostly crustaceans and insects. It is doubtful whether any species naturally infests man.

ECHINORHYNCHUS GIGAS.—The great thorn-head worm is a common parasite of the hog, living in the small intestine. It is a large white worm, the female of which reaches a foot in length, while the male is about one-third the size. It is doubtful whether it occurs as a human parasite, though a worm less than the fourth of an inch found in a man in Prague has been attributed to this species.

The Nematodes, or Thread-worms.

The nematodes, or thread-worms, are slender, cylindrical, and inarticulate, and usually more or less tapering toward one or both extremities. They have a distinct coelum or body-cavity, with thick muscular walls limited by a transparent elastic, chitinous integument, which is sometimes more or less distinctly and regularly transversely wrinkled. The alimentary canal extends the length of the coelum, with the mouth at the anterior extremity, and usually an anus at or near the posterior extremity. In some forms in the mature condition the intestine is atrophied and the anus absent. The sexes are distinct, and commonly the male is very much smaller than the female. The organs of generation occupy the coelum along the sides of the intestine. The female aperture is commonly situated ventrally near or in advance of the middle of the body, while the male aperture is at or in the vicinity of the anus. Mostly, the worms are oviparous, but many are viviparous. The development is direct, and usually the transformations are inconspicuous, so that the embryos mostly differ but little from the parent, except in the absence of the generative apparatus.

OXYURIS VERMICULARIS.—SYNONYMS: Ascaris vermicularis; Seat-worm; Pin-worm; Maw-worm; Maggot-worm; Thread-worm; Ascarides.

The seat-worm is the most common intestinal parasite of man, prevails everywhere, and is peculiar to him. It is a lively, wriggling creature which inhabits the small and large intestines and feeds on their contents. It frequently occurs in large numbers together, and in such cases incessantly makes its appearance, associated with multitudes of eggs, in the evacuations.

The female, which is ordinarily seen alone in the greatest abundance, is a white cylindrical worm tapering toward both extremities. The head end is thickened, and is provided with three prominent labial papillæ enclosing the mouth. The posterior end extends from the anal aperture in a long and straight, narrow, conical, sharp-pointed tail. The double uterine tube, distended with eggs, terminates in a vagina, the external aperture of which is situated ventrally near the anterior third of the body. The smaller male hardly tapers behind, but is incurved and ends in a short, blunt, conical tail. The penis is a single chitinous spicule, the end of which is usually seen projecting from the cloacal aperture.

The young seat-worms, in various degrees of growth and development, and the mature males are chiefly to be met in the lower portion of the small intestine, while the pregnant and mature females chiefly occupy the cæcum.

The seat-worm is exceedingly prolific, it being estimated that a single ripe female contains from 10,000 to 12,000 eggs, and these, it is suspected, may be renewed several times before her functions become exhausted. From time to time the ripe females proceed along the large intestine to the rectum, in which position they lay most of their eggs. These are discharged, together with many of the worms, in the feces.

The eggs are ovoid in shape and about 0.05 mm. long. After they are laid under favorable conditions the embryos are rapidly developed. Left in water, they soon die.

The investigations of the helminthologists of the day make it appear that it is necessary that the eggs of the seat-worm should be swallowed and pass through the stomach, in which the embryos are freed, before they can undergo development to sexual maturity. Moreover, observations go to show that infection may, and probably ordinarily does, occur from eggs scratched from the anus and conveyed to the mouth directly or by being applied to food from uncleanly hands. It is evident that itching of the anus, induced by the presence of the parasites in the rectum, often accompanied by itching of the nose and lips, may lead to alternate scratching of the parts and the transference of eggs from one to the other. Thus, too, uncleanly nurses who may be infested with seat-worms after scratching may handle food and infest children under their charge. Children are commonly more liable to the parasites than others, no doubt from the circumstance that they are less capable of avoiding the conditions favorable to infection. Seat-worms prevail in all conditions of society, but their prevalence is largely proportioned to the more or less uncleanly habits. Persons sleeping with others infested are liable to infection, especially if they are uncleanly and in the habit of eating in bed. Obvious hints to avoid the parasites are obtained by regarding the statements thus given.

SYMPTOMS.—The presence of a few seat-worms is usually attended with no obvious inconvenience, and they may remain unnoticed unless accidentally observed in the evacuations. The symptoms occasioned by them are in great measure proportioned to their quantity and the susceptibility of the patient. The most prominent symptom is excessive itching of the anus; often trifling or even absent during the day, it becomes very annoying and distressing in the evening or during the night. This periodic change appears to be due to the movement of the worms to the rectum, apparently induced by the position and repose of the patient and the increased warmth of the body in bed. Under these circumstances the patient attempts to relieve the incessant itching by scratching, and often by boring with the finger in the anus. In this way eggs become adherent to the finger-nails, under which they have been repeatedly detected, and may thus be inadvertently transferred to the mouth. Occasionally, some of the worms wander from the anus, and in women may thence penetrate into the vulva. The itching of the anus may induce more or less sexual irritation, which in the young may further lead to onanism and its attendant evils. Other symptoms of the presence of the parasites are itching of the nose and lips, restlessness in sleep, grinding of the teeth, startings, twitchings, and general nervous disturbance. When the worms are very numerous they may produce intestinal catarrh, with discharges of mucus, pain, and diarrhoea. In children especially they may give rise to more serious nervous symptoms, as epileptic fits and chorea.

TREATMENT.—Generally, persons are readily relieved of seat-worms. Epsom salt alone or with senna as a purgative, repeated once or twice, often answers to completely expel them. Castor oil, also alone or with a few drops of the oil of turpentine or of wormseed, is also an effectual remedy. The tincture of aloes, in the dose of from half a fluidounce to two fluidounces, once or twice repeated, the writer has found to fully answer the purpose. Besides the purgatives, medicated suppositories, in obstinate cases injections of olive oil, and enemata of a solution of castile soap introduced by means of an elastic tube, so as to wash out the entire length of the large intestine, may be employed.

ASCARIS LUMBRICOIDES.—SYNONYMS: Round-worm; Long round-worm; Maw-worm; Lumbricus.

The round-worm is the largest of the nematodes which ordinarily infest man, and is second only in frequency to the seat-worm. It is a well-known parasite, and prevails everywhere in all conditions of society. It is less lively in its movements than the seat-worm, and is remarkable for possessing a peculiar disagreeable odor, which is independent of the medium in which it lives. It inhabits the small intestine and feeds on the contents. It also infests the hog and the ox.

The round-worm is cylindrical, reddish or brownish, and tapering toward both extremities. The head end terminates in three prominent labial papillæ surrounding the mouth, and the tail end is short and conical. The female, as commonly seen, ranges from six inches to a foot in length, and is about a fourth of an inch in thickness. The ovarian tubes are long, thread-like, and tortuous, and, with the shorter, nearly straight, and wider uterine tubes, contain many millions of eggs. The genital aperture is situated ventrally near the anterior third of the body. The male is about half the size of the female, but is capable of considerable extension, and the tail end is incurved. The penis consists of a pair of slender, clavate, chitinous spicules, the ends of which protrude from the cloacal aperture at the root of the tail.

The round-worm is exceedingly prolific, it being estimated that the genital tubes of a large mature female contain the enormous number of 60,000,000 of eggs. The ripe eggs are laid in the intestine, and are discharged with the evacuations in great numbers, and often in considerable masses together. They are oval, about 0.05 mm. in length, and are provided with a thick shell and an additional tuberculate albuminoid envelope, usually colored by the intestinal contents.

The eggs of the round-worm after being expelled from the body are very tenacious of life, and under ordinary favorable circumstances they may remain in a condition capable of development for several years. Experiments have shown that they have great power in resisting the destructive influences of heat and cold, dryness, and the agencies of decomposition. In water and moist earth they have been retained alive for a year or two. When ripe eggs are placed in water the development of the embryo is observed to proceed very slowly, and is only completed after five or six months. The embryo while still contained within the egg sheds its skin and becomes provided with a tooth-like spine to the head end. The smallest examples of reputed round-worms found in the human intestine measured only about a line in length.

The further history of the round-worm is unknown, nor has it yet been positively ascertained in what manner man becomes infected with the parasite. Repeated experiments, not only on the hog and other animals, but on man himself, go to show that he is not directly infected by swallowing the recently-laid ripe eggs. It is rendered probable that the eggs are swallowed by some common but yet unknown minute aquatic animal, within which the embryo may undergo further development, and in this condition may be swallowed by man in drinking-water. In confirmation of the view that man becomes infected in the latter way, Davaine remarks that the "people of Paris, who drink only filtered water, are rarely infected with the round-worm, which is otherwise the case in the rural districts of France."

The round-worm is most prevalent in warm climates, and especially among the less-civilized peoples. The better classes among the more enlightened nations suffer comparatively little from the parasite, and it is the lower classes, especially the ill-fed and uncleanly, who are most afflicted. It is exceedingly frequent in the Orient, in Africa, the West Indies, and Brazil.

Most commonly, only a few round-worms—one, two, three, up to a dozen—occur together in the same person, but they often occur in considerable number, even to several hundreds. Not unfrequently they are found in association with seat-worms. They are more frequent and usually occur in greater abundance in children, perhaps in a measure due to the circumstance that they are less able to discriminate the conditions favorable to infection and avoided on other grounds by adults.

The natural and ordinary habitation of the round-worm is the small intestine, especially the jejunum, and it commonly only occurs in the large intestine, mostly dead, on the way to be discharged with the evacuations. Under disturbing circumstances, as the character of certain irritating food, the parasite is disposed to become restless and wander from its usual position. Not unfrequently it enters the stomach, and thence may ascend to the mouth or nose, and perhaps the first intimation of the presence of such an unwelcome guest is in its expulsion from the mouth. From the pharynx the worm may enter the larynx and trachea, or advance farther into the air-passages, giving rise to the usual symptoms of foreign bodies in these parts. Occasionally the parasite forces its way through the bile-ducts into the liver and gall-bladder, creating disturbance in those organs proportioned to the number and size of the worms and the extent of their progress. In the liver it may occasion inflammation and the formation of an abscess attended with all the usual symptoms of hepatitis. It has been reported that it may penetrate the intestinal wall and enter the peritoneal cavity, but it is generally regarded as doubtful whether the worm can do so in a healthy state of the intestine, but only where there may be ulceration or other similar condition.

SYMPTOMS.—The symptoms indicating the presence of the round-worm in the intestine vary with its numbers and with the age and susceptibility of the patient. In general, the presence of one or two worms is unattended with any marked disturbance, and is mostly unsuspected until the parasite is accidentally seen in the discharges. The ordinary symptoms are disordered appetite (usually increased), flatulence, hiccough, foul breath, dyspepsia, abdominal pains, itching at the extremities of the alimentary canal, furred tongue, darkening of the eyelids, and emaciation. The nervous symptoms are restlessness in sleep, unpleasant dreams, starting in fright, grating of the teeth, and muscular twitchings. In more aggravated cases, especially in children, epileptic fits may occur. If the parasites are numerous, they produce diarrhoea with copious mucus discharges, and may induce enteritis with all its attendant symptoms. When the worms wander into the stomach, they induce colic, nausea, retching, and vomiting, all of which disappear with the expulsion of the parasites.

TREATMENT.—The remedies employed for seat-worms often serve to expel the round-worm, and not unfrequently the two are discharged together. Wormseed, or the seed of Chenopodium anthelminticum, has been a favorite remedy for the round-worm, especially in children. The dose in these cases is one or two scruples of the powdered seeds in electuary with syrup or molasses, administered in the morning before breakfast and at bedtime for three or four days. It should be followed by calomel or other brisk cathartic. The volatile oil, in the dose of from five to ten drops in emulsion, may be used in the same manner.

A much-extolled remedy to destroy and get rid of the round-worm is santonin, given in doses of from one-third to one and a half grains three or four times a day, the larger dose being used only for adults. It should be followed by a purgative, for which a dose of castor oil answers a good purpose.

ASCARIS MYSTAX, the common round-worm of the cat and dog, has been reported as occasionally infesting man. It resembles the former species, but is much smaller, commonly from one to four inches in length, and has the head end furnished with a pair of lateral narrow, wing-like expansions of the integument. It inhabits the small intestine, and when present in man would no doubt induce symptoms like those of the ordinary round-worms which infest him.

TRIOCEPHALUS DISPAR.—SYNONYMS: Long thread-worm; Whip-worm.

The long thread-worm is a not unfrequent intestinal parasite of man, though rarely observed unless specially sought, as it ordinarily gives rise to little or no disturbance. It is common in England, Southern Europe, and the Orient. Davaine reports that half the cases of persons investigated in Paris were infested with it; it also occurs in this country. It inhabits the lower end of the ileum, the cæcum, and vermiform appendix, and feeds on the intestinal contents. It commonly occurs in small numbers, two or three to a dozen, occasions no evident inconvenience, and is rarely discharged with the evacuations.

The long thread-worm is yellowish-white and cylindrical, with the anterior half or more of the body attenuated in a hair-like manner. The female reaches about two inches in length, has the tail end conical, and the anus subterminal. The male is about two-thirds the length of the former, has the thicker portion of the body enrolled, and the tail end blunt. The eggs are laid in the intestine and discharged with the feces. The subsequent history of the parasite and its mode of infecting man remain unknown.

Only in cases where long thread-worms are numerous do they give rise to trouble. According to Leuckart, Pascal gives as constant symptoms of the presence of large numbers of the parasite, headache, redness of the face, prominence of the eyes, small, irregular, and intermittent pulse, and pains in the lower part of the abdomen.

The usual remedies addressed to the seat-worm and round-worm will most probably be equally applicable to the long thread-worm.

LEPTODERA STERCORALIS.—SYNONYMS: Anguillula stercoralis; Rhabditis stercoralis.

This is a minute nematode worm recently observed infesting French soldiers in Cochin China. It is about half a line in length, and inhabits the small and large intestine, and also penetrates into the biliary and pancreatic ducts. It occurs in myriads and occasions diarrhoea and dysentery. Another species, Leptodera intestinalis, nearly three times as large, has been noticed in smaller number associated with the former. The eggs of these worms are laid in the intestines, and both together are discharged in multitudes with the feces. They are probably introduced into man by drinking stagnant water, and undergo complete development after passing through the stomach.

It is probable that the remedies employed in the treatment of the familiar seat-worms and round-worms would be equally efficacious in the expulsion of these parasites.

ANCHYLOSTOMUM DUODENALE.—SYNONYMS: Strongylus duodenalis; Dochmius duodenalis; Sclerostoma duodenale.

This intestinal parasite, first noticed in Milan by Dubini in 1838, is of more dangerous character than any of the nematode worms previously described. In Europe, besides Italy, it was frequently observed among the workmen of the St. Gothard tunnel. It is exceedingly common in Egypt, and Bilharz found it in nearly all his post-mortem examinations of bodies. It probably prevails to a considerable extent in most tropical countries, including the East and West Indies and Brazil. There is also reason to suspect, from the nature of the affection it induces, that it may exist in the Southern States.

The Anchylostomum is a red, cylindrical worm, with the anterior extremity tapering and recurved. The head end, somewhat enlarged, encloses a capacious oral capsule armed with strong hook-like teeth. The caudal extremity of the female ends in a conical point, and the genital aperture is situated behind the middle of the body. The caudal extremity of the male ends in a trilobate pouch, within which projects the bispiculate penis. The female is from five lines to three-fourths of an inch long; the male is about half the size. The eggs are oval and measure 0.05 mm. long.

The worm inhabits the small intestine, especially the duodenum and jejunum, clinging tenaciously to the lining membrane by means of the armed mouth. It penetrates the mucous membrane to the submucous coat, from which it sucks the blood that forms its food. In the position of its attachment it gives rise to little ecchymoses. It often occurs in large numbers, even to hundreds and thousands. The eggs are laid in the intestine and are discharged with the evacuations. Externally, in water, the embryo undergoes development within the egg, and then escapes to lead for some time an independent existence. Subsequently, it is most probable that the worm obtains access to the human stomach by drinking standing water, and completes its development in the intestine.

The Anchylostomum proves to be a prolific source of wasting diseases in tropical countries, and is pernicious to an extent proportioned to the numbers infesting the intestine. By depriving the body of blood it produces a greater or less degree of anæmia. The affection begins very insidiously, and the general nutrition of the body may not be visibly disturbed until a late period. In moderate cases the disease is indicated by general paleness of the skin and mucous membranes, fatigue on slight exertion, and a tendency to palpitations and quickened pulse. In more severe cases there is constantly increasing debility, with increase of paleness, indisposition to exertion, excessive sleepiness, and feeling of coldness. Dyspeptic symptoms sometimes appear, and loss of appetite may alternate with ravenous hunger. Accompanying this there is often a disposition to eat innutritious articles, as coal, clay, wool, etc. Feeling of weight and oppression in the epigastrium and abdominal pains are frequent. In the advance of the affection shortness of breath appears, increased on exertion to violent dyspnoea. Emaciation becomes obvious in the later stage of the disease. In the worst cases the symptoms increase in severity, the patient becomes dropsical, is attacked with profuse diarrhoea and vomiting, and finally dies.

The severity of the affection is proportioned to the number of parasites present and the quantity of blood they consume and cause to be lost. Bad cases may end fatally in a few weeks, but generally the disease lasts for months, and where the patient is provided with abundance of good food it may continue for years.

The prognosis of the disease is rather unfavorable; if, however, the nature of the affection is ascertained before it has greatly exhausted the patient, and the parasites can be expelled, the result should be favorable.

We have thus far obtained but little information as to the best treatment for Anchylostomum. Calomel and turpentine have been recommended, and, as these are most powerful vermicides, we have reason to believe they would prove most effectual remedies.

In regard to the prophylaxis for Anchylostomum—and we may add in general for all parasites which gain entrance to man through drinking-water—all stagnant or standing waters should be filtered, so as to remove any source of infection, whether by eggs or free embryos of parasites or of larval forms existing within minute aquatic animals which serve as intermediate hosts to parasites. Standing waters, such as those of puddles, ditches, marshes, and ponds, more or less swarm with minute animals, all of which may be entirely removed by filtration. Even the water of cisterns and wells, if supplied from the free surface of the country, may not be free from minute animals, and especially eggs, and therefore requires filtration to be safe. Only spring and freely-running water of rivers and creeks and of lakes is commonly free from microscopic animals and their eggs, and therefore devoid of all danger in these respects.

STRONGYLUS LONGEVAGINATUS; S. bronchialis.—This nematode has been only once satisfactorily observed. Many occurred in the lungs of a boy in Germany, but the real cause of his death was not stated. The female worm is about an inch long, the male about five-eighths of an inch.

Certain worms previously discovered in the bronchial glands of a case of phthisis, and described under the name of Hamularia lymphatica, are regarded by Cobbold as the same with the former; but the descriptions of the two render this improbable. Treutler's drawing of Hamularia, as copied by Leuckart, looks like an Ascaris upside down.

EUSTRONGYLUS GIGAS; Strongylus gigas; Palisade-worm; Kidney-worm.—This worm, recorded in the catalogue of human parasites, is doubtful as such. Pertaining to the same family as Anchylostomum, as the common name indicates its usual habitation is the kidney. It is the largest of the nematodes, and is a long, cylindrical red worm, slightly tapering, and blunt at the ends. The mouth is enclosed by six rounded labial papillæ. The caudal extremity of the male ends in an inverted cup-like pouch, from which the penal spiculum protrudes. The female commonly ranges from one to three feet in length and from a fourth to nearly half an inch in thickness. The male ranges from six inches to a foot in length and from one to three lines in thickness.

The mature parasite is common in many fish-eating mammals, from which it is inferred that fishes are the intermediate host for the juvenile condition of the worm. It is frequent in the wolf, dog, mink, weasel, raccoon, otter, and seal. It also occurs in the hog, and is reported to have occurred in the horse, ox, and man. Usually it is solitary, and occupies one of the kidneys coiled upon itself. Under its influence the kidney is atrophied and reduced to the condition of a capsule of connective tissue, often containing bony spicules. It feeds on blood and on the purulent matter resulting from the inflammation it produces. The worm is occasionally found in other positions, as the mesentery, the abdominal cavity, the intestine, liver, urinary bladder, and lungs, but perhaps in most of these cases has been derived from its usual habitation. In this country the writer has repeatedly observed the kidney-worm in the mink, the dog, and the wolf. In one instance in the former animal he found a female and a male associated together in one kidney, which was reduced to the condition of a fibrous capsule containing in its wall a large radiated plate of bone.

The cases on record of the occurrence of this formidable parasite in man are of very early date, and are mostly doubtful as to the authentic nature of the worm, and are all unsatisfactory as to the attendant phenomena.

TRICHINA SPIRALIS.—The trichina, or flesh-worm, a minute nematode, is a common parasite of man, and from its wide prevalence and results may be regarded as the most dangerous of all. Perhaps from the earliest ages it has been dealing death freely and indiscriminately to our kind without its existence having been suspected until within the last half-century. Frequently, the affection, now named trichinosis, produced by its presence has been so prevalent in communities as to appear epidemic. The parasite was first discovered, and is commonly observed, as a little worm coiled up and imbedded in the flesh of man. In the same manner it is frequently seen in the flesh of the hog. In the adult or mature state it lives in the small intestine of both man and the hog, but its duration of life in this position is comparatively brief.

Trichinosis, or the disease induced by the introduction of trichinæ into the intestinal canal and the migration thence into the voluntary muscles, varies in symptoms and gravity with the number, condition, and position of the parasites and the susceptibility of the patient. The presence of trichinæ in the alimentary canal, though often accompanied by violent symptoms, is comparatively free from danger, whereas in the muscular system they not only produce the greatest suffering, but often the most disastrous results.

Man is ordinarily infected with the trichina by eating the raw or insufficiently cooked meat of the hog, or pork in any of its varieties of food. Infected meat often contains immense numbers of the parasite, a single ounce at times being estimated to contain from 50,000 to 100,000 worms.

The trichina was first distinctly noticed in the muscles of the human body by Paget in 1835, and was described by Owen with the name it now bears. It was subsequently observed under the same circumstances by other investigators. In 1846 the parasite was found by the writer in the muscles of the hog, but neither he nor others for some time afterward suspected the significance of the discovery. In 1860, Zenker of Dresden treated a supposed case of typhus complicated with excessive muscular pain and oedema. On post-mortem examination the muscles were found swarming with trichinæ, and to these the affection altogether was attributed. Nearly at the same time the investigations of Leuckart confirmed the relationship of the parasites as the cause of the disease. In 1862, Friederich first diagnosticated the affection and experimentally determined the presence of the worms in the living patient.

The trichina is also found infesting other animals of the same class besides man and the hog, especially the rat, mouse, rabbit, cat, and fox. Experiments further prove that mammals are generally more or less susceptible to infection with the parasite, though some appear to resist its extension to the muscular system, as in the case of the dog. The horse, ox, and sheep exhibit little disposition to artificial infection of the muscles, and hence from this circumstance and the nature of the food of these animals they are rarely found to be infested with trichinæ. In experiments on birds and lower classes of animals, though trichinæ were ascertained to advance in development in the intestine, they failed to invade the muscular system.

Ordinarily, it appears that while man is infected with trichinæ through the hog, this animal becomes infected by eating infested rats, mice, and cats, fragments of waste pork, and perhaps occasionally by feeding on the excrements of infested animals.

The trichinæ occupying the muscles are immature, and it is only after they are swallowed and the parasites are freed by digestion of the envelopes and pass into the intestine that they undergo development to sexual maturity. In this state the female is viviparous and gives birth to a multitude of active embryos, which immediately commence to migrate to the muscular system. As it is estimated that each female may give birth to upward of a thousand embryos, it is readily conceived to what an extent the body may become infested from eating a few ounces of trichinous pork.

The immature or larval trichinæ are also distinguished as muscular, and the sexually mature ones as intestinal, trichinæ, in accordance with their position in the two principal conditions.

Muscular trichinæ vary in condition from the embryo, which works its way among the muscular fibres or has obtained entrance into these, to the coiled-up worm lying quiescent in a capsule imbedded among the muscular fibres.

Infected flesh in the early state is scarcely distinguishable as such with the naked eye, but in old cases the trichina capsules become imbued with calcareous matter, and are thus rendered visible as minute white or grayish specks scattered through the red meat.

In the recent state of invasion the worms are found free among the muscular fibres or within these. Later, they appear mostly solitary and at rest, coiled within a fusiform mass of semi-liquid granular matter resulting from the degradation of the muscular substance. Subsequently, they become enclosed in an elliptical capsule, apparently derived from the myolemma of the muscular fibre they had entered. The capsules, situated among the bundles of sound muscular fibres, are arranged with their long diameter parallel with the latter. The trichina capsules commonly measure about one-fifth of a line long, and the coiled worm within is scarcely a half-line long.

If muscular trichinæ remain with their host, after a year or more they exhibit signs of decay. Commonly, little fat-globules appear at the poles of the capsules, and these become the seat of calcareous deposit. Finally, the worms die and undergo degeneration.

When meat with living trichina capsules is swallowed, the freed worms pass into the intestine, and here in the course of four or five days reach maturity.

The adult intestinal trichina is a minute, filiform white worm, thicker behind and tapering forward. The female is about an eighth of an inch long, and has the genital aperture at the anterior fourth of the body. The male is little more than half the length of the former, and has the caudal end provided with a pair of conical processes, between which is the genital aperture.

The ripe female trichinæ give birth to living embryos, and continue the function for about a month, after which they appear exhausted, ordinarily die, and disappear from the intestinal canal. The new-born embryos, about ¹/200 of a line long, quickly leave the intestine to be disseminated throughout the body. Penetrating the mucous membrane, they probably enter the blood-vessels to be carried onward by the blood-currents, and perhaps also, in part, directly migrate to their destination in the muscles. The latter mode of progress is rendered the more probable from the circumstance that the muscles contiguous to the intestinal canal, as the diaphragm and those of the abdominal walls, are commonly most abundantly infested with the parasites. In the muscles of the limbs they are sometimes noticed to predominate toward the extremities of the former, as if retarded in their course by the tendinous connections.

It would appear that muscular trichinæ, to be capable of producing infection—that is to say, of further development—must have reached a certain stage, corresponding with the encapsulated condition, before they are swallowed. In this stage they may remain within their host probably for a year or two.

Children seem to suffer less in proportion to the quantity of trichinous meat they eat than adults, and they appear less susceptible to muscular invasion of the parasites. The difference is probably in a measure due to the greater susceptibility of the intestinal canal and the consequent production of more copious diarrhoea in children, with more complete expulsion of the worms.

SYMPTOMS.—In general, the effect produced by eating trichinous meat is proportioned to the number and condition of the trichinæ ingested and to the susceptibility of the patient. A few of the parasites may pursue their entire career and die within their host without ever exhibiting any obvious evidence of their presence. Sometimes the symptoms of trichinosis are obscure or trifling, sometimes sufficiently well marked, but moderate, and often they are more or less striking and violent. The period of incubation of the affection varies from a few hours to a week or more, and the duration of the disease also varies—both in a measure proportioned to the number and condition of the parasites.

In mild cases of trichinosis the patient may pass through the course of the disease without being confined to bed, and in a few weeks may be regarded as convalescent. The majority of cases pursue a slow course of from six or seven weeks to three or four months. A fatal termination is frequent, and is most common from the fourth to the sixth week, and appears mainly to be due to the loss of respiratory power. Fatal cases rarely happen after the seventh week.

From a few hours to a few days after eating trichinous meat the patient may be seized with dyspeptic symptoms—nausea, cardialgia, flatulence, eructations, and vomiting. These may be accompanied with complete loss of appetite, excessive thirst, bad taste, and fetid breath. There is also commonly a feeling of general uneasiness, with fulness of the forehead or headache, and feeling of weakness and fatigue to exhaustion or complete prostration. Neuralgic pains are felt in the abdomen and limbs, and the muscles generally are more or less relaxed and flabby.

Violent disturbance of the alimentary canal occurs only when large quantities of active trichinæ are taken with the food. The subsequent symptoms, due to invasion of the muscular system, may, but do not necessarily, accord in degree with the former.

Diarrhoea usually comes on early, and the evacuations, at first more consistent, become thin and clay-colored, like those of typhus or like the rice-water stools of cholera. In the severest cases the patient may die in this stage from extreme exhaustion and with all the appearance of cholera. Sometimes the diarrhoea subsides and gives place to obstinate constipation.

The muscular symptoms induced by the invasion of the trichinæ may be trifling or moderate, varying to a most violent character. They commonly appear after a week, and later up to the sixth week. The muscles become more or less swollen, hard and tender to the touch, or highly painful under pressure. Motion is extremely painful, and the patient usually lies in a helpless state with the limbs flexed—adults on the back, children on the side. Difficulty, with pain, in chewing and swallowing ensues, and even complete trismus, due to the presence of the parasites in the muscles of mastication and deglutition. Difficulty of breathing also arises from the presence of the trichinæ in the respiratory muscles, especially the diaphragm and those of the larynx. Even movement of the eyes is painful, due to the parasites in the orbital muscles. Bronchial catarrh comes on early, attended with hoarseness and asthmatic cough.

Fever may be absent in mild cases of trichinosis, but is considerable in the severer forms, though not in the first few days. The pulse accords with the increase of temperature.

Profuse sweating is a common symptom of the affection, commencing early and continuing throughout. Generally there is considerable decrease in the quantity of urine, which is highly colored.

Adults suffer with insomnia, while the reverse state prevails in children, who commonly lie in a soporose condition. Formication and dilatation of the pupils are frequent symptoms.

Oedema is a characteristic and pathognomonic symptom of trichinosis, and is seldom so slight as to escape attention. It commonly appears in the eyelids and face about the end of the first week, and may disappear after several days, to recur after several weeks. It usually commences in the limbs in the second week, and is more marked and persistent, and increases, especially in severe cases.

Peritoneal and pleuritic irritation and inflammation, with bronchitis and pneumonia, are not unfrequent complications in the more aggravated form of trichinosis.

Most cases of the disease reaching the seventh week advance in convalescence, while those of mild character by this time have recovered, except from the weakness and emaciation, which remain as evidences of serious illness.

Trichinosis in children is distinguished by greater mildness, less danger, abundant oedema, less muscular pain, a dormant condition, and more rapid convalescence.

The distinct recognition of trichinosis is difficult in isolated cases, but becomes more evident where it occurs in numbers, as in an entire family or in large portions of a community. The proof that the patient has partaken of trichinous pork helps to establish the diagnosis.

In the beginning of severe cases of the affection symptoms of a more or less violent gastro-intestinal catarrh are commonly present, often associated with slight fever and almost invariably excessive perspiration. Muscular lameness, both in mild and severe cases, is an early symptom. The disease is distinguished from cholera by the profuse perspiration and the peculiar muscular symptoms; from ordinary rheumatism by the gastro-intestinal catarrh and general exhaustion. With the appearance of oedema of the eyelids and face at the end of a week the diagnosis becomes more certain. The further progress of the affection is so characteristic that its distinction can scarcely remain in doubt. The general prostration, the violent muscular symptoms, the bronchial catarrh, the hoarseness and dyspnoea, the profuse sweating, and the sleeplessness, render the case pretty clear.

In the prognosis of the disease no positive conclusion can be derived from the severity or early appearance of the initial symptoms. Commonly, the more speedily they occur and the more violent they are, the less favorable will be the prognosis, while the later they appear, the more propitious it is. Long-continued diarrhoea is especially unfavorable, while a profuse diarrhoea at the beginning is to be viewed as a fortunate event. The prognosis is more favorable in cases in which sleep and the appetite are maintained, and in those in which the disturbance of the respiratory organs is slight. A favorable termination of the affection is the rule with children.

TREATMENT.—The treatment of trichinosis is not generally promising in favorable results. No means have yet been discovered to destroy or remove trichinæ which have migrated from the intestinal canal. While the parasites continue within the latter we may have reasonable hope of expelling them from the body by means of the usual remedies for intestinal worms. Experience, however, with these remedies has not been in accordance with expectations. In the mean time, until some more potent vermicide is discovered applicable to the destruction and removal of trichinæ from the intestine, we are disposed to place most reliance on such purgatives as oil of turpentine and castor oil and calomel and jalap. Subsequently, a good nutritive diet with wine is recommended to preserve the life of the patient until the affection has reached that period when the parasites become capsulated and there is no longer danger from them as irritants.

As a preventive of trichinosis, besides the avoidance of pork or its varied preparations of ham, sausages, etc. when it is known or suspected they may be infested, thorough cooking of meats is a certain means. A boiling temperature surely kills all animal parasites, but care is requisite that large pieces of meat should be cooked sufficiently long that the desired heat may extend to the interior throughout. The writer may add that it was in a slice of boiled ham, from which he had partly made his dinner, that he first discovered trichina in the hog.

Of the nematode worms there are many species of comparatively long, slender proportions, which constitute the family of Filaridæ. As parasites they rarely occupy the interior of the intestinal canal, except by way of transit, and live in most other organs and tissues of the body of both vertebrate and invertebrate animals.

FILARIA MEDINENSIS.—SYNONYMS: Dracunculus; D. medinensis; Medina-worm; Guinea-worm.

The Medina-worm has long been recognized as a parasite of man, and by competent authorities has been regarded as the fiery serpent which afflicted the children of Israel in the wilderness of Judea. It prevails in the tropical regions of Africa and Asia, and thence has been introduced into tropical America. It is ordinarily observed as a long, white, cord-like worm, situated beneath the skin in any part of the body, but mostly in the lower limbs, and especially in the vicinity of the ankle. Though a frequent parasite, only the female is known. In the mature condition it is nearly uniformly cylindrical, and ranges from eighteen inches to three or four feet in length and less than a line in thickness. The head end is rounded and furnished with a little papillate plate, in the centre of which is situated a minute oral aperture. The caudal end is conical and incurved. The intestinal canal is atrophied and without an anal aperture. The coelum is mainly occupied by a capacious uterus filled with free embryos. A generative aperture appears also to be absent, and the young can only escape by rupture of the parent.

Experiments made about a dozen years since in Turkestan by Fedschenko, at the suggestion of Leuckart, have shown that when the embryos of the Medina-worm are introduced into water containing the familiar little crustacean cyclops, they penetrate into this, and within it undergo transformation into the larval stage. The subsequent history of the larval worms remains unknown, but from what we have learned of the history of many parasitic worms it is reasonable to suppose that if the infested cyclops is swallowed in drinking-water, it may explain the presence of the mature worm in the human body. The young worms, liberated from their crustacean host by digestion in the stomach, probably enter the intestine, and thence migrate to their destination. In the young condition, advancing to maturity, the worms have been found in all parts of the body except within the cranium and eyeball. They appear to migrate in the course of the least-resisting connective tissues, along the route of the principal blood-vessels, until they reach the surface of the body.

Usually, a single worm is found in a person, though cases occur where several, to a dozen or more, are present. Commonly, the parasite is solitary, though two or three may be associated together. When deeply seated the Medina-worm ordinarily produces but little discomfort, though in some cases its movements are accompanied with more or less severe pain. It also gives rise to inflammation and the formation of an abscess, in the purulent matter of which the worm lies bathed. The removal of the worm, when accessible, by the proper surgical aid is followed by complete relief.

It is evident that filtration of the drinking-water would be a certain prophylaxis for the Medina-worm.

FILARIA SANGUINIS.—SYNONYMS: Filaria sanguinis hominis, Lewis; F. sanguinolenta; F. Bancrofti, Cobbold.

Another species of Filaria, a more dangerous parasite of man and indigenous to the tropics, is of frequent occurrence, though of comparatively recent discovery. It has been observed in India, Africa, Brazil, and the West Indies. It is commonly seen in the embryonic condition, living in the blood of patients affected with elephantiasis and certain other diseases, and is also found in the urine. In this early condition it is a minute worm, scarcely more than the ¹/100 of an inch in length, and occurs together in immense numbers.

In the sexually mature condition the female filaria is a white hair-like worm three or four inches in length, living in the lymphatic vessels distally to the glands, especially in those of the lower limbs and scrotum. The embryos after leaving the parent pass into the lymphatic stream, and thence into the circulating blood. According to recent observations of Manson, they enter the blood in the evening and increase in number until midnight, after which they decrease and disappear by morning, from which time during the day they remain absent from the circulation. The investigations of the same authority have shown that when the blood of infected persons is sucked by mosquitoes these insects also imbibe the embryos, which subsequently undergo transformation in the mosquitoes into the larval state. In this condition the filariæ may be transferred to water, by drinking which man may become infected with the parasites. The larvæ introduced into the stomach appear thence to make their way to the lymphatics, within which they undergo further development to maturity, and thus remain a long time.

The presence of the worms in the lymphatics, with their numerous brood in the circulating blood, gives rise to hæmaturia and chyluria. As results of the obstruction of the lymphatic currents, the parasites induce inflammation, suppuration, lymphatic abscesses, buboes, lymphangiectasis, oedema, ascites, chylous hydrocele, elephantiasis,³ and certain cutaneous affections.

³ Several years since, with the view of ascertaining the presence of parasitic worms, the writer examined the blood of a case of elephantiasis under the charge of T. G. Morton, but none were detected. From what we have since been informed of the habits of Filaria sanguinis, the absence of the parasites may have its explanation in the circumstance that the blood examined was withdrawn in the daytime.

TREATMENT.—While the treatment of the affection induced by the Filaria sanguinis is varied and uncertain, the prophylactic measures are obvious and certain. Under favorable conditions of bright light, high temperature, and abundant food the stagnant waters of tropical countries are especially prolific of the minute forms of animals which harbor parasites. It hence becomes evident that all such waters, whether obtained from puddles, ponds, tanks, or cisterns, should be filtered before being used for drinking. Boiling is also effectual in destroying all the animal life of waters, and thus rendering them innocuous so far as parasites are concerned.

Several other species of Filaria have been found in the human body, but are little known and very rare in their occurrence.

FILARIA LOA.—This species occurs in Western Africa, on the Gaboon River, and is perhaps more frequent than now commonly supposed. It is an active worm, little more than an inch in length, and is usually found beneath the conjunctiva of the eye. It probably also occupies other positions, and a missionary on the Gaboon informed the writer that he had extracted one from the back of one of his own fingers. Its presence produced an intense burning pain. The negroes are reported to extract the worm by means of a thorn. The worm has also been observed in Brazil and the West Indies.

FILARIA RESTIFORMIS.—Under this name the writer recently described a large Filaria reported to have been withdrawn from the urethra of a man in West Virginia. It was obtained by C. L. Garnett, and sent, together with an account of the case, to the Army Medical Museum of Washington, where it is now preserved. It was a red cylindrical worm, twenty-six inches in length, tapering at the head, and thick, incurved, and obtusely rounded at the tail end.⁴

⁴ Proceedings of the Academy of Natural Sciences, Philada., 1880, p. 130.

FILARIA OCULI HUMANI; FILARIA LENTIS.—A few cases are on record of the occurrence of little worms in the aqueous humor and crystalline lens of the human eye, to which the accompanying names have been applied.

FILARIA TRACHEALIS.—Recently some minute worms found by Rainey in the trachea and lungs have been described under this name.

In conclusion, the writer acknowledges his indebtedness for much of the information of this article to the articles on "Intestinal Parasites" and "Diseases from Migratory Parasites" in Ziemssen's Cyclopædia of the Practice of Medicine, and to Glazier's Report on Trichina and Trichinosis.