CHAPTER XXXIII. 

 RABIES. 



THIS is a disease of dogs and wolves, but is communicable to man 

 and domesticated animals. The virus, whatever it may be, resides in 

 the saliva and nervous structures. It is destroyed by a temperature of 

 50 C. In man the period of incubation is usually from three weeks to 

 three months, but may be shorter or may extend over one year. 



Bites about the face and those with marked lacerations are particu- 

 larly serious. Bites of rabid wolves give about four times as great 

 a mortality as those of dogs. In the dog there are two types of the 

 disease dumb rabies and furious rabies. 



By inoculating rabbits subdurally with an emulsion of the brain or 

 spinal cord of a rabid animal, and successively the medulla of this 

 rabbit subdurally into other rabbits, we finally so increase the virulence 

 of the infection that rabbits die in six days. Beyond this it is im- 

 possible to increase the virulence and it is termed "fixed virus." To 

 attenuate this virus the spinal cord of the rabbit is removed and is dried 

 over caustic potash. The cord is divided into segments about one 

 inch in length. Drying for about fifteen days seems to entirely de- 

 stroy the virus. 



To prepare the material for prophylactic injections a small portion 

 of the cord is emulsified and injected subcutaneously. The German 

 method is to commence with a cord that has been dessiccated only eight 

 days. At first injections are given daily, and it is possible to inject 

 three days' cords by the sixth day. 



The treatment lasts for about twenty days. In the diagnosis of 

 rabies in dogs it is preferable to preserve the animal so that the develop- 

 ment of the symptoms may be observed. In case the dog has been 

 killed, it may be possible to make a diagnosis by means of the Negri 

 bodies. These are round or oval bodies from i to 2o// in diameter, 

 which may be found in the nerve-cells, especially those of the cornu 

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