GENERAL DISEASES. 99 



usually occurs in the horse as the result of the bite of a 

 dog. Whether it can be transmitted from an infected 

 horse to a healthy one by biting is uncertain, but probably 

 it can. 



The poison is especially virulent in the saliva. Eecently 

 M. Pasteur has demonstrated the existence of a special 

 vegetable parasite in the blood of rabid animals, and to the 

 presence of this germ and its multiplication in the body he 

 attributes this infective disease. 



Incubation. — In the horse, the period of incubation varies 

 from two weeks to forty days. 



Symptoms. — Begin with great restlessness, excitability, 

 and distress. In some cases there is first observed a lack 

 of power over some of the voluntary muscles, especially 

 those of the hind extremities, or some amount of tonic 

 contraction in the muscles of the back or neck. The 

 excitability is soon much increased, the animal becomes 

 frantic, and attempts in his fury to destroy everything 

 within his reach. In some instances he bites savagely at 

 the seat of the injury. 



The temperature is raised 2° or 3° ; the pulse is accele- 

 rated, its volume is increased, and the artery is firm and 

 hard ; the respirations are accelerated, and the appetite is 

 lost ; the animal is acutely sensitive to the slightest stimuli. 

 A flash of light or a sudden noise will bring on a paroxysm 

 of fury. 



There are convulsive twitchings of the superficial muscles; 

 difficulty in swallowing ; a characteristic hoarse cough ; 

 abundant flow of saliva from the mouth ; paralysis of the 

 posterior extremities may gradually supervene. The remis- 

 sions and paroxysms in the horse are not so marked a 

 feature as in the dog. In the horse, the remissions are of 

 much shorter duration, and the fits of violence are more 

 aggravated and prolonged than in the latter animal. As 



7—2 



