THE TAENIA echinococcus (Echinococcus granulosis) lives in the intestine of the dog, from which its egg is transmitted to the human stomach. From here, the young embryos penetrate the walls of the digestive tract, and the blood carries them to various other organs of the human body, for instance, the liver, lungs, and kidneys. At the site of its new abode the larvae of this parasite form hydatid cysts, which may attain the size of a child's hand. The walls of the cyst are composed of an outer layer, of chitin, the ectocyst, and an inner, parenchymal layer, the endocyst, in which are found the heads of the future parasites with their hooks and suckers. Very often one large cyst contains numerous daughter cysts. Besides this unilocular type, one sometimes finds the multilocular type, composed of several small cavities, filled with a gelatinous substance. Hydatid cysts have been often found