Chap. IX.] HOOKS OF CESTODA. 287 



hooks, or of bristles. The former are well developed 

 in some of the Cestoda, as in Trenia soliuni (the 



Fig. 12U. berpiila vermic'i/an's, showing the coiled Tube, and the 



Animal protruded. 



tapeworm\ where the head is surrounded by a 

 circlet of recurved chitinous hooks, by means of which 

 the animal fixes itself to the mucous membrane of the 

 intestine of its host ; the presence of these is the cause 

 of the difficulty found by the practitioner in attempting 

 to expel the parasites from the human intestine. 



