PL A TYHELMTNTHES 2 1 1 



movement by contraction of its muscles. The eggs are set 

 free by its rupture. If, as may happen in various circum- 

 stances, they are now swallowed by a pig, or, as occasionally, 

 by man, their shells are dissolved in the alimentary canal 

 and a little spherical six-hooked embryo or onchosphere is set 

 free from each. This bores its way from the intestine of 

 the pig into its blood vessels and is carried to the muscles 

 and other organs, where it loses its hooks, increases in size, 



Fig. 130. — A proglottis of Tania solium 

 with the reproductive organs at the stage 

 of complete development. 



c.s., Cirrus sac ; excr., excretory canals \g.o., genital 

 opening; n.c, nerve cord; ov., ovary; sk.g-., 

 shell gland; t. t testes; v.d., vas deferens; ut., 

 uterus ; vag-., vagina; y.g., yolk gland. 



and becomes a bladder-worm or cysticercus. The wall of 

 this becomes tucked in at one spot, forming a pouch, on 

 the inner wall of which the suckers and hooks of the 

 future head appear. No further change takes place unless 

 the flesh of a pig infested with such bladder-worms (known 

 as "measly" pork) be eaten raw or "underdone" by man. 

 When this happens, the stimulus of the new surroundings 

 causes the head to be turned inside out. The bladder is 

 digested, but the head fixes itself and begins to bud off 



