TAPE-WORMS 



225 



hooks are liberated. They bore their way from the in- 

 testine into the muscles or other structures, and there 

 encyst. They lose their hooks, increase in size, and 

 become passive, vegetative, asexual " bladder-worms." A 

 bud from the wall of the bladder or proscolex grows into 

 the cavity of the same, and forms the future " head " or 



Fig. 121. 



Front end of the head of Tcenia solium, showing four adhesive suckers 

 and a circle of fixing hooks. The natural size is that of an ordinary 

 pin's head. 



scolex. This is afterwards everted, ajid then the bladder- 

 worm consists of a small head attached by a short neck to 

 a relatively large bladder. 



When man unwittingly eats " measly " pork — that is, 

 pork infested with bladder-worms — an opportunity for 

 further development is afforded. The bladder is lost, and 

 is of no importance, but the '* head " or scolex fixes itself 

 to the wall of the intestine. There it is copiously and 



15 



