CESTODA OR TAPEWORMS. 



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serious disturbances. This second period of Cestode- 

 life is known as the ' Cvstic ' or ' Bladder-worm ' 

 stage. The cyst is uroduced in the following way : 

 the ova released from the ripe proglottides are 

 disseminated over the grass and into water. The 

 ' cystic ' host eats these ova with its food, and the 

 embryo Gestode (fig. 20) is released by the action of 

 the gastric juice, which dissolves the egg-shell This 

 embryo is a minute body provided with six little hook- 

 lets. It bores its way through the walls of the intes- 

 tine into the blood-system and is carried along by 

 the blood; eventually it reaches its destination, which 

 may be either the liver, brain, peritoneum, kidnev, 

 lungs, and other internal organs. Once on its 



igs, and other internal organs. 



Fig. 21. 



Bla elder- worm. Cysticercus type. 



' feeding-ground/ the embryo becomes converted 

 into a small bladder-like body, which may grow to a 

 considerable size — the cyst or hydatid (fig. 21). The 

 bladder is full of liquid, and in it, according to the 

 group of tapeworms, will be found from one to many 

 small opaque points. These latter are scolices — heads 

 of future tapeworms. This cystic form may remain for 



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