The diagnosis is only complete when portions of the worm come away with the feces. Their shape, as each small segment is more or less elongated in proportion to its breadth, enables us to form an idea of the length of the entire worm ; when they are long and broad, we may conclude that it is of considerable length ; when short and broad, the remaining portion is probably not great ; when narrow as well as short, the fragments come away from near its head or fixed extremity. It is a curious cir cumstance, in regard to the two species of twnia, that they rela tively abound more in certain localities ; the bothriocephalus is usually imported into this country, and is soon expelled from the body, while the solium among us lives and thrives.
b. Round worms (lumbrici), seldom solitary, are chiefly lodged in the small intestines, where their presence does not seem to give rise to any very marked symptoms ; occasionally, however, they are productive of mischief by wandering into the appendix caeca, the gall-duct, or the stomach ; and, when lodged high up in the canal in childhood, are apt to give rise to convulsive affections— both chorea and epilepsy.
c. Threadworms (ascarides) are found sometimes in enormous numbers, and reside chiefly in the rectum. They are very com
mon in children, and produce irritation of the mucous membrane, as shown in picking the nose, scratching the anus, &c.: sometimes they crawl into the vagina and cause much annoyance. It does not appear that they give rise to any derangement of _health, but they are commonly associated with depraved states of the alimen tary canal and unhealthy secretions.
Another intestinal worm might be mentioned, the Trichocephalus dispar, but that it does not seem to be associated with any morbid phenomena, and when passed would be readily taken for an ascaris. For similar reasons we have not alluded to the various forms of filaria, one of which, the " guinea worm," is seldom seen in this country ; nor to the Trichina spiralis, some times found in the voluntary muscles ; nor to the distoma, which, as the " liverfluke," is so common in sheep ; or the cysticercus, which in the pig produces what is called '• measly pork.' The two last are more rarely met with in the human species. The Strongylus gigas, found, I believe, only in the kidney. may be the cause of various symptoms referable to the disintegration and absorption of the organ, but cannot be in any way diagnosed during life.