Schistosoma Japonicum in China 



217 



consisted of first finding a case of the disease and then hunting 

 in the neighborhood of the patient's home for a snail somewhat 

 similar to Blanfordia nosophora. On August 11, 1922, such a 

 snail was found in large numbers on the shore of a small terminal 

 canal near which many cases of schistosomiasis japonica resided. 

 Examination of these snails by crushing their shells revealed a 

 five per cent, infection with cercariae morphologically similar to 

 that of Schistosoma japonicum. A mouse immersed in water 

 containing these cercariae was found, thirty-one days later, to 

 harbor adult forms of Schistosoma japonicum in the portal and 

 mesenteric veins. Snails of this type were exposed to miracidia 

 of Schistosoma japonicum and at intervals thereafter were killed, 

 and showed in serial section the development of the sporocyst and 

 cercaria forms of the parasite. 



The snail which acts as the intermediate host of Schistosoma 

 japonicum in the Soochow district is an operculate gasteropod 

 averaging 6.4 mm. in length by 3.0 mm. in breadth. Its shell is 

 acuminate in form, has seven spirals, is dextrally coiled, is of 

 dense consistency and has closely set ridges running perpendicular 

 to the spiral groove of the shell. Its shell differs from that of 

 Blanfordia nosophora in its greater density, its ribbed surface 

 and its greater breadth in proportion to its length. These fea- 

 tures place the Chinese intermediate host in a different genus 

 from the Japanese host. Owing to the difficulty of correctly 

 classifying the members of the genus to which this snail ap- 

 parently belongs, we have referred it for classification to an ex- 

 pert malacologist, Mr. Bryant Walker of Detroit. 



The snail was found in the Soochow district on the shore of 

 small canals, particularly terminal ones. It was usually found 

 just above the water's edge, and in fewer numbers just beneath 

 the surface of the water. It preferred secluded spots protected 

 from the sun. It was not found in the rice fields, probably be- 

 cause in this district the fields are from four to six feet above the 

 level of the canals, and are therefore too dry for the snail's 

 existence. 



In order to check up by biological phenomena the morphologi- 

 cal similarity of the forms of Schistosoma japonicum developed 

 from Japanese and Chinese material, we exposed the Japanese 

 intermediate host to miracidia from a Chinese patient, and the 

 Chinese intermediate host to miracidia from a dog infected with 



