. Animal parasites and human disease. Medical parasitology; Insects as carriers of disease. Fig. 76. Egg and ciliated em- Little is known of the life history of any species except the Chinese fluke, C. sinensis. The eggs (Fig. 76A) are of charac- teristic shape, and hatch in water into miracidia (Fig. 76B). The encysted cercarise of this fluke (Fig. 77A) have been found in the subcutaneous tissues and muscles of 12 different species of fresh-water fish. The cysts, which are very small, measuring only about by mm. {j^-^ by if^(T of an inch), are usually more abundant in the superfi- c
. Animal parasites and human disease. Medical parasitology; Insects as carriers of disease. Fig. 76. Egg and ciliated em- Little is known of the life history of any species except the Chinese fluke, C. sinensis. The eggs (Fig. 76A) are of charac- teristic shape, and hatch in water into miracidia (Fig. 76B). The encysted cercarise of this fluke (Fig. 77A) have been found in the subcutaneous tissues and muscles of 12 different species of fresh-water fish. The cysts, which are very small, measuring only about by mm. {j^-^ by if^(T of an inch), are usually more abundant in the superfi- cial than in the deeper tissues, bryo of Chinese fluke, Opisthorchis Although cysts Can be found in sinensis. X 700. (After ,^ , , i fish throughout the year, the younger ones are more frequently met with in late summer and early autumn. When infected fish are eaten, according to experiments re- cently made with animals by Kobayashi, the larval flukes escape from the cysts (Fig. 77B) within three hours, and in fifteen hours they may] already have reached the bile duct and gall bladder. The parasites reach maturity and eggs are found in the faeces of the host within 26 days. The young flukes have a spiny cuticle until nearly mature, but the spines finally disappear. The first intermediate host Fig- 77. Larv« of Chinese fluke; A, . , u-i, 1'T oercaria encysted in fish; B, larva freed mto which newly hatched Clll- f.^^ <,yst; mouth in oral sucker; v. s., ated embryos penetrate is not ventral sucker; ex. v., excretory vesicle; ,-11 J. 1. J. ph., pharynx; int., intestine. certainly known yet, but Kobayashi believes it is one or more of the several species of snails of the genus Melania, especially Melania libertina. These snails have been found to harbor cercarise which bear a distinct resem- blance to the young encysted larvae of the Chinese fluke, and they are abundant in rivers and swamps of regions where the liver infection prevails. It is probable that
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