Page:Tropical Diseases.djvu/907

XLV] Echinostomum. In length it is 4-6 mm. by 0·75-1·35 mm. in breadth. It is attenuated posteriorly. The acetabulum is much larger than the oral sucker. The genital pore opens separately a little behind the half-way point between the pharynx and the acetabulum. Each testis has an anterior and a posterior lobe. The ovary is globular.

Nothing is known about the life-history of the parasite, beyond the fact that a miracidium hatches in about ten days after the eggs have left the host.

This parasite is found in the intestines of natives in the Malay States, but probably is not normally parasitic in man. The body is 12 mm. long by 3 mm. in greatest breadth, and 1·3 mm. in thickness. Both ends of the body are rounded. There is a row of 43 stout spines round the circumoral disc; they vary in size; those on the ventral are 0·07 mm. and those on the dorsal surface 0·05 to 0·16 mm. in length. The oral sucker comprises one-third of the total diameter of the circumoral disc; it communicates with the spheroidal muscular pharynx by a thin-walled portion 0·175 mm. long. The œsophagus measures 0·04 mm. in length, and bifurcates near the pharynx. The main gut branches are simple and end blindly at the hind end of the body. The ventral sucker, 0·9 by 0·75 mm., is several times larger than the oral. The testes are tandem and are deeply lobed; they are situated in the middle of the body behind the ventral sucker. The cirrus pouch is well developed, and extends behind the level of the fundus. The ovary has a smooth surface, and lies immediately in front of the anterior testis, 0·85 mm. behind the ventral sucker.

The ordinary tapeworms, Tænia saginata (Fig. 196) and Tænia solium, and their cystic forms, are common enough in the tropics and sub-tropics, their distribution being regulated by the presence or absence of their proper intermediary hosts—the ox in