100 THE INTERNAL PARASITES OP 



thus the hogget or a calf swallows the egg of a gid tape- 

 worm, turnside will be the consequence ; but if the 

 herbivore swallows the eggs of the hydatid tapeworm, 

 properly so called, hydatids will be the result. And so 

 on, with other creatures which happen to ingest the ova 

 of different and appropriate parasites. 



To hares and rabbits the dog thus communicates 

 another bladder- worm disease ; and we ourselves are 

 also liable to become infested with hydatids from the 

 same source. 



All these evils may be readily overcome, if the advice 

 have offered be duly acted upon. 



To be sure, neither the helminthologist, nor any other 

 true man of science, need personally reckon upon any 

 adequate return for sacrifices of time, made in the 

 interests of the public good ; nevertheless, when abundant 

 light has been thrown upon points of great practical 

 importance, it is a legitimate prerogative on the part of 

 the scientist to demand that the results of his labours 

 shall be utilised for the benefit of others. 



The largest tapeworm liable to reside in the dog is a 

 parasite chiefly derived from the sheep ; that is to say, 

 the sheep acts as the principal intermediary bearer of the 

 larval cestode, which latter acquires tapeworm -maturity 

 when it is taken into the stomach and intestines of the 

 dog along with flesh-food. The entozoon in question is 

 the margined tapeworm. 



This worm {Taenia marginata) reaches a length of 

 from five to eight feet. It is an abundant species, 

 occurring probably in fully 25 per cent, of English dogs 

 that are not less than one year old. In Denmark it occurs 

 in 14 per cent. ; and in Iceland, according to Krabbe, 

 in no less than 75 per cent, of the native dogs. 



