THE ROUND WORMS AND PLAT WORMS 129 



Coenurus cerebralis, which is found in the bladder-worm 

 stage in sheep where it is often lodged in the brain, the cys- 

 ticercus may reach the size of a hen's egg. It is a fre- 

 quent cause of death to sheep. 



Echinococcus in the bladder-worm stage may attain an 

 enormous development. Some specimens reach the size 

 of a child's head and weigh several pounds. Each .cyst 

 may produce a large number of worms. The tape-worm 

 stage of this form is, curiously enough, a small worm of 

 only four segments, usually found in the dog. The blad- 

 der-worm most commonly occurs in sheep, but there are 

 many cases where it has been found in man, and has not 

 infrequently been the cause of death. Echinococcus is 

 common in Iceland and some parts of Australia where 

 sheep and dogs are kept. Living in too intimate relations 

 with dogs greatly increases the chance of becoming in- 

 fected with this terrible parasite. 



