SCHISTOSOMA 



211 



Adult flukes of different species differ widely in regard to the 

 organs or tissues of the host which they attack. The majority 

 of species live in the alimentary canal, in any part from mouth 

 cavity to anus, some species being very closely limited to certain 

 portions. Next to the alimentary canal the liver is the organ 

 most frequently chosen, and then the lungs. The urinary or- 

 gans, body cavity, bloodvessels and other organs and tissues 

 are chosen by some species. The brain and nervous system are 

 only accidentally invaded. One species lives in the eustachian 

 tube of an aquatic animal, 



V.s..f9 



-gijn.c. 



another in the conjunctival 

 sac in the eyes of birds. 



The flukes which infest man 

 may be divided for conven- 

 ience into four groups, the 

 blood flukes, the lung flukes, 

 the liver flukes and the intes- 

 tinal flukes. Altogether over 

 20 different species have been 

 found in man, but only those 

 which are common or impor- 

 tant will be considered in the 

 following pages. 



Blood Flukes 



The most important flukes 

 parasitic in man are three 



species of Schistosoma (or iriu.64. Blood fluke, Schistosoma fecma- 



Bilharzia) which live in the tobium; male ( $ ) carrying female ( 5 ) in 



, 111 1 r j.1. I, ventral groove; int., intestine; gyn. c, 



large bloodvessels Ot the ab- gynecophoric canal or ventral groove; m., 



dominal cavity. mouth; v. s., ventral sucker. X 8. (After 



Schistosoma is one of the 

 few genera of flukes in which the sexes are separate. The 

 relation of the sexes is one of the most remarkable in nature. 

 The mature male worm (Fig. 64) has a cyUndrical appearance 

 due to the fact that the sides of the flat body are folded over 

 to form a ventral groove. In this groove, projecting free at each 

 end but enclosed in the middle, is the longer and slenderer 

 female, safe in the arms of her lord. While young the sexes hve 



