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

by Unknown

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.