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Chapter III. 



THE LIVEE-FLUKE OF THE SHEEP. 



Fasciola [Distomum) hepatifa. 



The adult liver-fluke is a flat unsegmented worm, about an 

 inch and a half long, living in the bile-duets of certain 

 domestic animals, and notably in those of the sheep, in which 

 it gives rise to the destructive disease known as liver-rot. It 

 very rarely occurs in man. 



The animal is hermaphrodite, and its eggs, which have 

 thick chitinous shells, are deposited in enormous numbers 

 in the bile-ducts of the sheep or other host, from which 

 they pass into the alimentary canal, ultimately escaping with 

 the fseces. From these eggs, if deposited in damp places 

 or in water, larvse are produced which lead a free existence 

 for a short time, but very soon become parasitic within 

 the body of Limncea truncatula, an amphibious snail. Two 

 or. more asexually produced generations now succeed : and 

 the last of these encyst on grass. These encysted forms are 

 swallowed with the grass by sheep, and passing into their 

 bile-ducts become the adult sexually mature flukes. 



This alternation of sexual and asexual generations, living 

 parasitically within different hosts, is a very characteristic 

 feature in the life history of many parasitic worms. 



I. THE MATUEE LIVER-FLUKE. 



Slit open the bile-ducts in the liver of an infected sheep, 

 and transfer the living flukes to a dish of warm salt-solution 

 (•75 per cent.) to clean them. 



1. Inject the excretory system of one fluke, and the 



