102 



THE INTERNAL PARASITES OP 



professional man to realise the fact that the same entozoon 

 in its larval or vesicular state attains a size many thou- 

 sand times exceeding that of the parasite in its adult 

 condition. 



Harmless when full-grown, it is fearfully destructive to 

 life in the juvenile stages of growth. To be sure, its bad 

 effects are chiefly witnessed in the human subject ; but 



Fig. 22. Hydatid Tapeworm and Echinococcus-Head 



cattle, sheep, horses, and swine occasionally perish from 

 the presence of the larva? within their vital organs. 



If it be asked how all this mischief is brought about, 

 the briefest answer suffices to explain the matter practi- 

 cally. The herbivorous animals and ourselves get the 

 echinococcus disease by swallowing the eggs of the 

 hydatid tapeworm. 



Here is a representation of the parasite (Fig. 22, A). 

 It exhibits the head segment with its four suckers and 



