Previous Work on B. japonica 137 



Army in Egypt for dealing with an outbreak of bilharziosis amongst the 

 troops stationed at Kasr Nil Barracks during 1912. In an article in 

 1915 by another authority in Egypt the following occurs : " Any small 

 puddle or hole may become defiled, and in a very short time the water or 

 mud is alive with miracidia, which may become applied to the bare feet, 

 arms or hands, penetrate the skin directly and so lead to infection." 

 " Certain evidence we have none nor has any intermediate host ever been 

 discovered." 



Keviewing the bilharzia problem in the Spring of 1912, in the light of 

 Fujinami's experiments and the repeated failures to infect monkeys and 

 other animals with the miracidia of B. hamatohia, I concluded that the 

 time had come to renew the attempt made by earlier workers to establish 

 a molluscan transmission for this parasite. 



In view, however, of the lack of success which had attended the 

 previous efforts of Sonsino, Lortet and Vailleton, and others to follow the 

 miracidia, a new method of approach seemed called for. 



The occurrence of Bilharzia magna in Cercocebus fuliginosus rendered 

 it not improbable that by subjecting monkeys of this species to immersion 

 in water containing the various cercariae, found in the endemic area, a 

 positive result might eventuate. As B. hcBinatobia occupied a peculiar 

 habitat in man and did not naturally infect any other animals a negative 

 result might follow. In any case such an empirical method would 

 obviously involve the purchase, transport and maintenance of a large 

 number of monkeys or necessitate an unusually prolonged investigation, 

 for which the necessary financial support was not likely to be forthcoming. 



The experiments of Fujinami and Miyagawa appeared to me to open 

 up a possibility that a morphological clue might be established by which 

 the bulk of cercarite of unknown origin could be excluded microscopically ; 

 thus bringing the experimental use of monkeys within practical limits. 



Was there any outstanding feature which distinguished the adult 

 distomes from the adult bilharzia worms and which had, in all likelihood, 

 persisted from the sexless cercarial stage? In the cercaria there are 

 organs, like the tail, which are purely larval structures, and others, like 

 the suckers and the gut, which persist from the body of the cercaria 

 through adult life. In some cercariae, however, the gut has not yet formed 

 although there is an oral sucker. 



The suckers are, both as regards structure and position, very similar in 

 distomes and bilharzias. The alimentary canal is, on the other hand, 

 markedly different. The bulk of the distomes have a separate muscular 

 pharynx. There is no pharynx in the bilharzia worms. 



If this distinction were one which persisted from the cercarial stage 

 then it afforded an easily determined morphological clue by which one 

 could immediately exclude the vast majority of cercariae, which are 

 distomes. 



It might be that the pharynx, originally separate, became fused with 



