THE DISEASES OF SHEEP 313 



Montana. The writer promptly diagnosed the dis- 

 ease as gid, or turn sickness, caused by the encysted 

 parasites called Taenia Coenurus. This worm is 

 the fruit of a tape worm that infests dogs or wolves. 

 The eggs pass from the dogs or wolves and are 

 taken in by the sheep on the grass or in their drink- 

 ing water. They hatch within the sheep and the 

 young worms pierce the walls of the stomach, gain- 

 ing the blood where they travel until they reach the 

 brain, where they undergo a change, developing 

 heads and making large bladders in which to live. 

 It is necessary that the sheep should die after these 

 cysts have reached a certain stage of development 

 so that some dog, fox or wolf may feed upon the 

 dead sheep's head and thus take into its own sys- 

 tem the parasites which become established there 

 as regular tapeworms. Thus the round is contin- 

 ued. The tapeworm within the dog or wolf reinfects 

 the grass, the sheep become affected and die to in- 

 fect more dogs (if there are any). Now the way 

 this hydatid affects sheep is by pressing upon the 

 brain substance and absorbing it until the nervous 

 system is quite deranged, the sheep is stupid, it 

 turns steadily round and round, always the same 

 way, neglects food and dies. 



The disease is somewhat prevalent in England 

 and Scotland in some years but is probably rare in 

 America, at least in a rather long experience the 

 writer is not sure that he has ever seen an instance 

 of it, but from his book lore he advised his neighbor 

 to dissect the next ailing sheep and look for the 



