156 THE PRACTICE OF VETERINARY MEDICINE. 



containing a large number of eggs : the egg is picked up by 

 the sheep whilst grazing or drinking; on reaching the stomach 

 its shell is readily dissolved, setting free a minute parasite, 

 which enters the circulation, by which it is carried along 

 until finally it reaches the brain, where it becomes encysted, 

 and sets up a considerable amount of irritation. It is most 

 likely to exist where sheep and dogs mix. Any part of the 

 brain may be attacked, but the hydatid usually locates itself 

 in the upper part of one hemisphere, or between the hemi- 

 spheres. The pin-like points on the hydatid penetrate the 

 covering of the brain, causing effusion, and sometimes 

 absorption of the bones. 



Symptoms. — The affected animal leaves the flock, walks in 

 a circular manner with the head carried on one side, when 

 the hydatid is located in one hemisphere ; when it is 

 situated between the hemispheres, the head is carried in an 

 elevated position, and the animal has vertigo. There is 

 softening, elevation, and partial absorption of the bones. 



Treatment. — Make an opening, and draw out the fluid and 

 the hydatid at the same time with a syringe. 



RABIES. 



Definition. — A disease of the nervous system characterized 

 by fever, a high degree of irritability and excitement, the 

 presence of spasm, a disposition to bite, great prostration, and 

 finally death. It was called hydrophobia, on account of in- 

 ability on the part of the sufferer to drink water, which 

 inability was supposed to be caused by dread of the liquid. 

 However, as the rabid animal has not the slightest dread of 

 water, and is. only prevented from taking it by spasmodic 

 action of the muscles of deglutition, it will be seen that the 

 term hydro23hobia is a misnomer, a far better name being 

 rabies (from 'rabio,' to rave). 



Man and all of the lower animals are liable to this 



