There are various kinds of worms known to • find a lodgment in the human body. The chief of them belong to two great classes: (1) the tape worms or band-worms, and (2) the round or thread worms. The scientific terms for these classes are cestodes or tmnize, and nematodes. Cestode is derived from a Greek word, kestos, meaning a band, and is therefore identical with the common word tape-worm ; tcenia is the Latin for a band or ribbon ; nematode is de rived from the Greek, nema,and means a thread. There are also found occasionally in man worms belonging to the trematode, or fluke class. Trjma is the Greek word for an opening, and the term was applied to the worm because it exhibits slickers which were thought to be mouths. Fluke means flat, and was used to describe the worm because of its shape.
It is the object of the following paragraphs to describe the principal examples of the above classes from which human beings suffer, along with the symptoms their presence produces, and the appropriate treatment in each case. The natural history of these animals forms a most remarkable and interesting chapter of science. On this account in the description of them some small amount of detail will be given.
(cestodes, kenice).—There are several species of tape-worm, namely, Tank solium, Tcenia mediocanellota, Tcenia iota or Bothriocephalus lotus, and Twnia echinocoecus. The two first are the commonest The TEenia solium (Pork Tape-worm) is re presented in Fig. 114. At a is the head, which is from the to the of an inch in dia meter—about the size of a small pin head. From the head there passes a slender neck, with cross strips, which gradually becomes broader and flatter till the body is reached. The latter part of the animal consists of a series of segments or joints (b, b), which are shown in the figure about the natural size. The complete tape - worm measures 7 to 8 feet in length, and towards the lower end the joints measure about of an inch broad, and inch long. There may be as many as 1200 joints in one tape-worm. Now it must not be under stood that this great length forms one in dividual; it con sists, properly speaking, of a colony of indi viduals. Each fully - developed joint is perfect in itself, and in dependent, hav ing within it the capacity for reproducing ita species, and be ing entitled to be regarded as a distinct animal. To each joint the term pro glottis is applied. To the long colony of pro glottides which, dependent from the head, go to form the tape worm, the term strobilus is plied. The head is called the notes, and is to be considered as the parent of the whole colony, as will be understood immediately. It
is by the scolex or head that the tape-worm is anchored to the mucous membrane of the tine in which it dwells. A head is represented magnified in Fig. 115, 1. It has a projection or proboscis (a) at the extremity, which is rounded by a double row of hooklets (1), there being twelve to fourteen booklets in each row.
18 The shape of a hooklet is represented in Fig. 115, d. A little above the middle of the head are four projecting suckers, three of which, c,c,c, • are represented in the figure, by which it is aided in maintaining its hold in the intestine.
Now let us trace the his tory of this parasite.
It may re main in the bowel of the in dividual whom it infests, and who is called its host or bearer, for many years, deriving its nourishment, not by a month,- for it has none, but by the passage through its soft body wall of some of the nourishing fluids by which it is bathed. During its lifetime it goes on shedding fully developed joints from its extremity, while its length is maintained by the continual forma tion of new joints between the head and those already formed. As new joints are produced, those already formed are pushed farther and farther from the head, becoming developed as they pass from the head, till in their turn they are separated from the rest of the strobilus and are passed by the person. The passage of the joints is a circumstance of great discomfort. A ripe joint, or proglottis, is filled with eggs, the seed capable of producing a multitude of other tape-worms, provided suitable soil is found for them. The eggs are contained in a branched structure in the joint, indicated in Fig. 114, and one joint, it has been estimated, may contain 45,000 eggs. When a joint is passed it is still able to elongate and contract, and at length is ruptured, by means of which the eggs are liber ated and scattered abroad. Each perfect egg contains a tape-worm, but in its embryonic or larval stage, in which it has little resemblance to the fully-developed worm. The embryo is only about the of au inch in breadth, and is inclosed within a thick brownish shell, which protects it from destructive agents, the shell resisting even ordinary chemical agents. The head of the minute embryo carries three pairs of hooklets instead of the crown of booklets of the scolex, and they are formed, not for holding on, but for boring and tearing. The eggs, then, containing such embryos are dispersed abroad. They get into sewers, into water, and in one way or another are scattered also over fields.