Th us cleanliness in every respect, and thorough cooking of all meat, are effectual preventives of the occurrence of tape-worm.
II. (Nematodes) are different in appearance from tape-worms. They are not flat like the latter, but present characters re sembling earth-worms, having elongated round bodies marked with cross ridges. They have a mouth at one end, an anus near the other extremity, and an alimentary canal connecting the two. They offer this great distinction to the tape-worms, that the sexes are separate, the male being smaller than the female. Their natural history is not so well known as that of the tape-worms. It seems certain, however, that they have several stages of existence like the tape-worms, and that these different stages are passed in different "hosts" or "carriers." It seems evident that they cannot grow and multiply in the intestinal canal of man. The seeds which a female will discharge in a day number many thousands, and, if it were pos sible for their eggs to be hatched in the intes tinal canal of man, the number of worms of which he might be the victim would be be yond estimating, and would produce symptoms such as are never experienced. It appears, therefore, that the ova or seed must be ex pelled from man's intestinal canal, must de velop in some other place or animal, and must return to man in a more advanced stage in drinking-water, along with food or flesh, or in some other way, before the mature animal can be produced. Where these secondary stages are produced is not known.
The Common (Ascurz;3 lum bricoides) is shown in Fig. 121, and resembles in appearance the common earth-worm. The females measure from 10 to 14 inches in length, and from to inch in thickness, while the males are 4 to 6 inches long and correspondingly narrower. The female produces eggs about the to inch in size to the number of 160,000 daily. The eggs are contained within a shell and pass out in the faces. It would seem that the round-worm of man and that which infests the hog are the same, and that perhaps the hog is the animal in which some stage of the parasite is ac complished.
Impure drinking-water may be a source of infection.
Usually only six or eight of the worms inhabit the intestinal canal, though cases are on record of one person harbouring a multitude.
It is the upper and middle part of the small intestine that the worm frequents, though it may wander upwards or downwards.
Symptoms.—Persons may har bour worms and yet manifest no indications of their presence. But symptoms of intestinal irritation may arise, such as colicky pains, sickness and vomiting, looseness of bowels, itching of the nose and anus. Convulsions in children are not infrequently caused by the irritation of worms. Epilepsy has been produced by them, and various other nervous diseases.
Treatment.—Sanionin, the ac tive principle of santonica, is the best remedy.
It is given in doses of from 1 to 3 grains for a child, and twice as much for an adult. It should be given in the morning in cream, and followed an hour or two afterwards by a dose of castor-oil.
Common (Oxyuris vertni cularie, Seat-worm).—This is specially the worm which plagues children. It is shown in Fig. 122, the female (a) and male (1,) magnified considerably. The female is from'} to inch long, and the male about half that size. They occur in the large intestine, specially low down.
They are often present in very large numbers, and may be passed in ball - like masses coiled up with one another.
In females they may pass out of the anus and into the vagina, setting up irritation there, inducing itching, excite ment, and discharge.
It appears that this worm may pass through its various changes of development in the same host. But the eggs, it seems, cannot be hatched in the lower bowel. A person, however, troubled with these worms may infect himself by the accidental conveyance of the eggs from the anus to the mouth. By scratching, the person may catch up eggs under the finger nails, the eggs pass into the stomach, and the action of the gastric juice enables the hatching to take place.