LIFE HISTORY OF SCHISTOSOMA JAPONICUM 



219 



S. japonicum in a species of Limncea in Japan. Miyairi and 

 Suzuki, in further work on the life history of this fluke, found 

 that after sporocysts have developed in the tissues of infected 

 snails rediae are produced, 50 or more from each sporocyst. 

 The long, coiled rediae crowd the liver and produce cercarise, the 

 latter reaching maturity in about seven weeks. If in autumn 

 the cercarise have become fully developed but have not left 

 the snails they remain in their hosts over winter. 



Leiper obtained development of the characteristic fork-tailed 

 cercarise in another small snail, Blanfordia (or Katajama) noso- 

 phora, common in the rice fields of Japan. There is an interest- 

 ing tale connected with 

 Leiper's experiments on 

 infection with these para- 

 sites. With great care this 

 investigator experimented 

 with the infection of snails 

 which he had imported 

 from Japan to work on in 

 his laboratory at Shanghai. 

 After having succeeded in 

 obtaining infection of the 

 snails, he teased out the 

 livers in water to liber- 

 ate the cercarise. Four 

 laboratory-bred mice, 

 which are difficult to ob- 

 tain in the Orient, were J^ } infected with Schistosoma - 

 immersed in the water 



in which the cercarise had been liberated, and a start was made 

 for England. But alas! a woman in a neighboring stateroom 

 objected to the presence of the mice so near and demanded their 

 relegation to the butcher's cabin, where three of them died. At 

 Aden the few remaining infected molluscs were sacrificed and 

 the last mouse was subjected to infection. A month later when 

 the animal was examined in the laboratory of the London School 

 of Tropical Medicine many blood flukes, males and females in 

 couples, were found in the portal bloodvessels (Fig. 68). 



It should be remarked in concluding this discussion of the 

 blood flukes that many snails, including members of the genera 



FIG. 68. Mesentery of mouse with blood- 



(After 



