tinal obstruction develop. There is obstinate constipation, and when the bowels are moved, the stools appear as thin, flat bands, often streaked with pus and blood. On physical examination a tumor may be detected.

Intestinal Parasites.

What are the most common varieties of intestinal parasites? The most common intestinal parasites belong to the order of vermes, of which there are two important classes-cestodes, or tape-worms, and nematodes, or round-worms.

Of the former the more important are the tenia solium, the tenia mediocanellata, and the bothriocephalus latus.

Of round-worms the most common are the ascaris lumbricoides, the oxyuris vermicularis, and the trichina spiralis.

The oxyuris vermicularis inhabits the large intestine, the tapeworms and the lumbricoides the small intestine; the trichina migrates from the stomach and small intestines into the muscles, setting up an irritative fever with special symptoms, the condition being known as trichiniasis.

What symptoms are occasioned by the presence of animal parasites in the intestinal canal?

The presence of worms in the intestinal canal of an otherwise healthy individual may occasion no appreciable disturbance. In other cases, however, there are evidences of gastro-intestinal derangement, capricious appetite, abdominal uneasiness, colicky pains, possibly diarrhea, nausea, vomiting, loss of flesh, debility, cachexia, irregular fever, disturbed sleep, gritting of the teeth, itching of the nose and anus, nervous manifestations, even epileptiform convulsions.

The diagnosis of intestinal worms depends upon the discovery of the parasites or of their ova in the stools.

Tenia Solium.

What are the characteristics of the tenia solium?

The tenia solium (Fig. 24) is a tape-worm having a small head, or scolex, and a slender neck. The head is of the size of a pin

head, and is surmounted by a circle of twenty-six hooklets, around which are four suckers. From the neck pass off segments, or proglottides, that progressively increase in size. The entire worm, or strobila, may be from seven to ten feet long and composed of from four hundred to six hundred segments. The tenia FIG. 24.

solium usually develops in man from the ingestion of "measly" pork or the flesh obtained from swine infected with the cysticercus cellulose, which in turn develops in animals that have swallowed the ova of the tenia solium.

Tenia Mediocanellata.

What are the characteristics of the tenia mediocanellata? The tenia mediocanellata, or unarmed tape-worm (Fig. 25) differs from the tenia solium in that the head, though surmounted by four suckers, is without hooklets. The tenia mediocanellata may attain a length of from ten to twenty feet, and be composed of from eight hundred to more than one thousand segments, which are longer and broader than those of the tenia solium

The tenia mediocanellata is transmitted to man by the raw flesh of sheep or cows, in which hosts the larvæ develop from the ova of the tenia mediocanellata.

Tape-worms are usually present in small numbers; there is often but a single worm; sometimes there are two or three.

About three months are requisite for the development of a tape-worm.

What are the characteristics of the bothriocephalus latus? The bothriocephalus latus (Fig. 26) sometimes called the tenia lata, is a cestode worm, with a club-shaped head and a filament

ous neck. On either side of the head is a longitudinal sucker. The mature segments present a characteristic stellate appearance, dependent upon the distention of the uterus with ova. The worm may be from fifteen to twenty-five feet in length, and constituted of from three thousand to four thousand segments. It is thought to be derived from fish or fresh-water molluscs.

Ascaris Lumbricoides.

What the characteristics of the ascaris lumbricoides?

Lumbricoid or round worms inhabit the small intestine. Small worms, embryos, or ova, are supposed to gain access

a, natural size; b, head, magnified; c, ovum, magnified.
Ascaris lumbricoides (v. Jaksch).

to the alimentary canal of man through drinking water, and in some instances to be conveyed by the fingers to the mouths of

those engaged in cleansing privies or otherwise handling excrement, but the exact history of their development is unknown.

Mature worms are from eight to fifteen inches in length, are attenuated at both extremities, and resemble common earthworms. Lumbricoid worms may be present in varying numbers, from one to a dozen or more. They are usually multiple, and in rare instances may be so multitudinous as to occlude the intestine. The worms may find their way into the stomach, and be expelled by vomiting. They may pass from the esophagus into the larynx and trachea. They have in this way caused suffocation in children. They may cause occlusion of the bileduct or pancreatic duct, and, though rarely, suppuration of the liver or of the pancreas. They may also leave the intestine by way of a perforation, causing peritonitis or fecal abscess.

Oxyuris Vermicularis,

What are the characteristics of the oxyuris vermicularis? Oxyures vermiculares, seat-worms, thread-worms, or spool-worms, are from one-eighth to one-half of an inch long. They infest the large intestine, especially the rectum. The worms find their way out of the anus, and give rise to intense itching. FIG. 28.

Oxyuris vermicularis, natural size (Vierordt).

Sometimes they gain access to the vagina, and occasion unpleasant symptoms. The parasites may be present in the bowel in large numbers; they are often found in the stools in tangled masses, resembling bunches of thread.