212 



THE FLUKES 



apart, but as soon as sexual maturity is attained they couple 

 together and spend the rest of their lives in this manner. 



Unlike the liver flukes, the blood flukes do not develop great 

 numbers of eggs all at once, but instead develop them one by one 

 and have only a few in the oviduct at any one time. Such a 

 method of reproduction is facilitated, of course, by the constant 

 juxtaposition of the male and female worms. The blood flukes, 

 live correspondingly much longer than the liver flukes, often 

 persisting for many years. 



Schistosoma hsematobium. — The most important species 

 from the pathogenic point of view is Schistosoma hwmatobium 

 (Fig. 64) . This parasite is common in the' countries surrounding 

 the eastern end of the Mediterranean, southern Asia and many 



Fig. 65. Eggs of Schistoma; A, terminal spined egg of S. hosmatobium from 

 urine; B, lateral spined egg of S. mansoni from faeces; C, egg of S. japonicum, with 

 only rudiment of spine; note developed embryos in all. X about 200. (A and B 

 after Looss, C after Leiper.) 



parts of Africa, especially the east coast. In Egypt over half the 

 population are said to be infected, and in an examination of 

 54 boys in the village of El Marg, near Cairo, 49 were found 

 infected. 



These flukes, about one-half inch in length, abound sometimes 

 in hundreds in the abdominal veins of their host, living espe- 

 cially in the portal vein and its various branches. The eggs of 

 the worms, which are oval with a stout spine at one end (Fig. 

 65A), and about 0.16 mm. {j^js of an inch) long, are carried to the 

 small vessels on the surface of the urinary bladder. By means 

 of the sharp spine they penetrate to the wall of the bladder and 

 are voided with the urine. As the eggs enter the bladder they 

 cause a certain amount of bleeding, resulting in a bloody urine. 



