170 ZOOLOGY FOR MEDICAL STUDENTS chap. 



other species, and the spine which is small and inconspicuous is lateral 

 in position (Fig. 77, B, 3, and Fig. 90, D). The eggs reach the exterior 

 by way of the intestine as in 5. mansoni and the sporocyst stage is 

 passed in a water-snail Hypsobia ( = Katayama) with a long pointed 

 conical shell. 



As regards other flukes parasitic in man note should be taken of 

 three, normally inhabitants of Eastern Asia but liable to be carried to 

 other parts of the world by immigrants. 



Clonorchis 



Slender-shaped Liver-flukes which are placed in this genus are fre- 

 quent parasites in. China and Japan and cause serious damage to the liver. 

 They reach a length of from 6 mm. to 20 mm. The fresh-water snail into 

 which the miracidium bores is apparently a Melania and the cercariae 

 find their way into the bodies of various fresh-water fish where they 

 remain encysted amongst the connective tissue and muscle until swal- 

 lowed by the mammalian host. The latter is commonly a man, dog, 

 cat or pig. 



Paragonimus 



A common and destructive parasite of man (as of dogs and cats) 

 in China, Korea and Japan, this fluke may occur in various organs of 

 the body but its favourite haunt is the lung, in whicii as it grows in size 

 it forms large cavities. It measures up to about 12 mm. in length and 

 is thick-bodied, nearly circular in cross section. The eggs pass away in 

 the sputum to which they give a characteristic brown colour. The 

 life-history is of the normal type, the incriminated water-snail being a 

 Melania, except that as in Clonorchis the cercaria enters an intermediate 

 host before encysting. Normally this appears to be a fresh-water crab, 

 but as these are not commonly used as food by man in districts where 

 the parasite is common the suspicion is entertained that some other 

 animal, possibly a fresh-water fish, may take the place of the crab. 



Fasciolopsis 



This parasite, which inhabits the intestine of the pig and of man 

 in Eastern Asia — from India to China and the Malay Archipelago — is 

 mainly of interest from its being the largest fluke known to occur 

 in man, reaching a length sometimes of 75 mm. Its life-history is 

 uncertain. 



