INTERNAL PARASITES OR WORMS. 



349 



The following are found in the dog: T(£nia mar- 



ginata^ T. ctccumerina, T. ser- 



rata, T. echinococcus^ T. so- 

 lium, and Bothriocephalus la- 



tus, the last two being common 



to man and the dog. 



The first three are the most 



common : T. fnarginata, the 



intermediate host of which is 



the sheep, may attain a length 



of eight to ten feet ; T. cucu- 



inerhia, the most common, ten 



to twenty inches in length, with 



a very small head, the segments 



getting very gradually larger 



from before backward ; T. ser- 



rata, intermediate host the hare 



and rabbit, twenty to forty 



inches in length. 



To illustrate how tape- worm 

 is propagated and how one ani- 

 mal may prove a source of dis- 

 ease to many, we may mention 

 that a larval or immature form 

 {Coenurus cerebralis) of a tape- 

 worm exists in the sheep's 

 brain. If this be taken into 



the dog's stomach it develops fig. 35.-t^nia solium (Stonk- 

 into a mature tape-worm, the 



^ c, generative orifice; e, water vascu- 



eggS of W^hich, if swallowed by lar canals ; g, ovarian duct ; h, 



ovarian receptacle ; i, branched 



the sheep in drinking-water, ovarium. 



