2l6 



UNSEGMENTED WORMS 



Type The Liver Fluke {Distomum hepaticutn) 

 The adult fluke lives as a parasite in the liver and bile 



ducts of the sheep, causing 



liver-rot." 

 flukes, it 

 occasional 

 sometimes 



e.v 



FiG.i 1 6. —Structure of liver fluke. — After 

 Sommer. From ventral surface 

 branched gut (g.) and the lateral 

 nerve [l.n.) are shown to the left, the 

 branches of the excretory vessel {e.v.) 

 to the right. 



m.. Mouth ; ph., pharynx ; g., lateral head 

 ganglion ; v.s., ventral sucker ; c.s., position 

 of cirrus sac. An arrow indicates the ex- 

 cretory aperture. 



Unlike most 

 has many 

 hosts — it 

 occurs in 

 cattle, horses. deer, 

 camel, antelopes, goat, 

 pig, beaver, squirrel, 

 kangaroo, and rarely in 

 man. The animal is flat, 

 oval, and leaf-like, almost 

 an inch in length by half 

 an inch across the 

 broadest part, reddish 

 brown to greyish yellow 

 in colour. As the word 

 Distomum suggests, there 

 are two suckers — an an- 

 terior, perforated by the 

 mouth ; a second, im- 

 perforate, a little farther 

 back on the mid-ventral 

 line. 



There is a muscular 

 pharynx and a blind 

 alimentary canal which 

 sends branches through- 

 out the body. The food 

 is the blood sucked from 

 the liver of the host. 

 From a ganglionated 

 The collar round the pharynx, 

 nerves go forward and 

 backward ; of those 

 which run backward, the 

 two lateral are most im- 

 portant. Although the 

 larva has eye spots to 



