SCHISTOSOMA MANSONI 



2 77 



consider them as indicative that the miracidium has developed into 

 a sporocyst, but Looss considers them to be degeneration products. 



The Bilharzia mission, under R. T. Leiper, sent to Egypt by the 

 War Office early in 1915, reports that cercariae of bilharzia type were 

 recognized in four of the commonest fresh-water molluscs around 

 Cairo. 



With material obtained from naturally infected Planorbis boissyi 

 acute bilharziosis was experimentally produced in rats, mice, and 

 monkeys. Infection takes place experimentally through the skin and 

 also through the mucous membrane of the mouth and oesophagus. 

 The miracidium, after entering the mollusc, develops into a sporocyst. 

 This gives rise not to rediae, but to secondary sporocysts, which, in 

 turn, produce cercariae. These, like the adult worm, differ from other 

 distomes in lacking a muscular pharynx. 



Schistosoma mansoni, Sambon, 1907. 



According to Manson, Sambon and others, the eggs with lateral 

 spines belong to a species different from Schistosoma hcematobium. 

 Infections with this species only are said to 

 occur in the Congo, Southern States of North 

 America, West Indies (Guadeloupe) and Brazil 

 (Bahia). The following characters, according to 

 Flu, differentiate this species : (i) In the male 

 the transition from the anterior portion of the 

 worm to the lateral fields (the infolded portions 

 which form the gynaecophoric canal) is not a 

 gradual one as in Schistosoma hcematobium y 

 but in this case the lateral fields rise suddenly, 

 almost at right angles to the anterior portion. 

 (2) The ovaries have a well-marked convoluted 

 course as in no other schistosome. (3) The 

 ootype is symmetrical in reference to the long 

 axis of the body, its duct being lateral on the 

 ventral side (Looss' explanation of this we have 

 already given). (4) The worms live exclusively 

 in portal vein and tract. (As lateral-spined eggs 

 occur also in the bladder, this is not exactly true.) 



FlG. 175. Ovum of 

 Schistosoma hamatobium, 

 Bilh., with miracidium, 

 which has turned its an- 

 terior end towards the 

 posterior end of the egg. 

 275/1. (After Looss. 



Schistosoma japonicum, Katsurada, 1904. 

 Syn. : S. cattoi, Blanchard, 1905. 



Male. Eight to 19 mm., but extreme limits are 5 to 22*5 mm. Con- 

 sists of a short fore-body, separated by the ventral sucker from the 

 hind-body. The ventral sucker is stalked and somewhat larger than 



