414 



THE ANIMALS AND MAN 



digested in the intestine of its host. It has no eyes or other 

 special sense-organs, nor any organ of locomotion. Thus 

 its body is very degenerate. The life-history of the 

 tapeworm is interesting, because it lives in two hosts 

 during its life. The eggs of this parasite pass from 

 the intestine with the excreta, and to develop must 



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FIG. 206. Trichina spiralis, encysted in muscle of a pig. (Greatly en- 

 larged.) 



be taken into the body of some other animal. In the 

 case of one of several species infesting man this second host 

 is the pig. In the alimentary canal of the pig the young 

 tapeworm develops, to bore its way later through the walls 

 of the canal and become imbedded in the muscles. There it 



