vain to distinguish these worms from each other by their hooks. The wolf or the dog follows the flock of sheep, scatters the proglottides or the eggs in their way, and the sheep, browsing on the grass with the eggs attached, become infested with their most dangerous enemy.
To arrest this disease, only one thing is necessary, to destroy by fire the head of every sheep attacked by the “gid.” The rest of the animal may be eaten without danger.
Pouchet did not succeed in giving sheep the “gid” at first, for the very simple reason that he employed the eggs of the Tænia serrata, instead of those of the Tænia cœnurus; he had confounded the two species. The cœnurus of the sheep is a true calamity when it spreads in a country. The animal attacked by it is lost, and the mischief may be indefinitely propagated by giving as food to dogs the head of the sick animal, with thousands of young tæniæ enclosed within each.
There exists a singular cestode which bears the name of Echinococcus. We give a figure of the echinococcus of the pig, slightly magnified, and an isolated scolex (Figs. [55] and [56]). In its first form it is composed of closed sacs, which grow to the size of a nut, and sometimes to that of an orange. It usually lodges in the liver of the pig, but establishes itself also in man. We have been assured that part of the population of Iceland have been attacked by it. The abundance of this parasite in that country is attributed to the want of cleanliness, and the number of dogs that they keep around them. The echinococcus becomes a tænia in this animal. It scatters the eggs with its dung, leaving them directly or indirectly on plants which the Icelanders eat; for they gather for
food certain mosses, sorrel, cochlearia, dandelion, &c., from the midst of the plains in which live flocks of sheep guarded by dogs. The eggs are scattered everywhere on plants or in the water.
Fig. 55.—Isolated scolex of the Tænia echinococcus from the pig.
