CHAPTER V. 

 SCHISTOSOMID^E. 



THE Schistosomidce as causes of disease are of great 

 importance. Several species are known in the lower 

 animals, such as Schistosomum indicum in horses in India, 

 S. crassum in cattle in Egypt and Malaya. In these the 

 spine on the ovum is terminal. Two definite species are 

 known to occur in man, S. hcematobium and S. japonicum. 

 S. hcematobium (Bilharzia hcematobia) maybe taken as the 

 type of the bisexual trematodes. The male is the larger 

 and is a broad, flat worm bent longitudinally on itself, so 

 that the two lateral edges are in contact or even overlap. 

 A tube is thus formed, and in it the female is found. This 

 tube is known as the gynaecophoric canal. There are 

 two prominent suckers. The anterior, oral, sucker is 

 terminal. The oesophagus is short and straight, and the 

 bifid intestine anastomoses with its fellow frequently. 

 The contents of the intestine are usually black. The 

 testicles are rounded masses and variable in number, 

 apparently even in the same species. The vasa deferentia 

 unite and open near the posterior sucker, and the female 

 opening is situated opposite it, in the usual position in 

 which the males and females are found. The outer 

 dorsal surface of the male is studded with projecting 

 bosses, so that the surface is much roughened, and prob- 

 ably this aids in the movements of the worm in the 

 blood-vessels and in the retaining of a selected position 

 when it is attained. The male is 15 to 18 mm. in length, 

 and when flattened out 3 to 5 mm. in breadth. The female 

 is longer, so that at each end it projects from the gynae- 

 cophoric canal. It is 20 mm. in length, and is a thin, 

 cylindrical worm only 0*25 mm. in breadth. The suckers 



