their shells by the action of the gastric juice, and there issues an embryo singularly armed. As we have before said, it carries in front two stylets in the axis of the body, and on the right and left sides two other stylets curved at the end, which act like fins. These embryos bore into the tissues as the mole burrows into the soil. The middle stylets are pushed forward like the snout of the insectivore, and the two lateral stylets act like the limbs, taking hold of the tissues and forcing the head forwards. In this manner the embryos perforate the walls of the digestive tube.
An egg of the Tænia solium may be swallowed by a man instead of passing into the stomach of the pig. It is hatched in his stomach precisely in the same manner, and the embryo takes up its lodging in some enclosed cavity. Some have been found in the eye-ball, in the lobes of the brain, in the heart, or in the muscles. We have lately read an account of the effects produced by one of these wandering worms, on a man who died after suffering from a peculiar disturbance of the mind. Two spirits seemed to haunt and speak to him, the one a German, the other a Pole. Filthy images were called up before his imagination. At the post-mortem examination, cysticerci were found to occupy the sella turcica, near the commissure of the optic nerves. One of these was alive, the others were calcified. Two others in a similar condition occupied a lobe of the brain.
Man harbours not only the Tænia solium, but another species very similar, which naturalists have only learned to distinguish from it during the last few years, the Tænia medio-canellata. We give a magnified representation of the scolex, that is to say, of the head of this
worm, which has no crown of hooks in the middle of its four suckers.
Fig. 53.—Tænia mediocanellata.
This solitary worm is introduced by means of beef, and the cysticercus, during its abode in the cow, manifests already the peculiar characteristics which enable us to recognize the species, that is to say, no crown of hooks, but four suckers, and in the middle of them, some blotches of pigment. Leuckart fed a calf with eggs of this tænia, and at the end of seventeen days, the animal died of acute miliary tuberculosis, produced by the great abundance of cysticerci. This second species, which had been always confounded with the preceding, and which is nevertheless the more common, has therefore a different origin from the Tænia solium. Observations made quite recently in the north of Africa demonstrate this. Great difficulty had sometimes been felt in explaining the presence of the tænia in persons who had not eaten pork. This embarrassment arose from the confusion of the two species, and this confusion is the more easy as the head of the colony must necessarily be found in order to distinguish them.
Scharlau, at Stettin, found tæniæ in seven children who had been fed, on account of anæmia, with raw meat. The tæniæ were those of this species. We have ourselves found them in children to whom the use of raw meat had been prescribed.
We do not think it necessary to speak here of a third species of tænia (T. nana), which also lives at our