426 DISEASES INVOLVING NERVOUS SYSTEM 



these symptoms are not always present. Occasionally the 

 diagnosis is extremely difficult and cannot be made dm'ing the 

 life of the animal. Generally the psychic, sensory, and motor 

 disturbances, the fatal termination, and the negative post- 

 mortem are indicative. As a rule, however, a positive diag- 

 nosis can be made only by microscopic examination or experi- 

 mental inoculation. In cases of doubt it is best to confine 

 the animal for a day or so for observation, during which time 

 there usually develop sufficient symptoms to make the diag- 

 nosis highly probable. 



The microscopic examination, which is highly valuable, 

 consists in the examination of properly prepared and stained 

 brain tissue, particularly of the hippocampus, medulla 

 oblongata, and cerebellum. In practically 98 per cent, of the 

 cases of rabies which died or were killed in the advanced 

 stages of the disease, peculiar cells, the so-called Negri bodies, 

 are found. The presence of the Negri bodies indicates rabies 

 while their absence tends to disprove its existence. 



Diagnostic Inoculations. — An emulsion is usually obtained 

 from the medulla oblongata of an animal which died or was 

 killed because rabies was suspected. This is injected sub- 

 cutaneously or subdurally into rabbits or sometimes pups. 

 Intra-ocular and intramuscular inoculations have also given 

 successful results. Usually in from two to three weeks after 

 the injection the experimental animal dies of typical rabies 

 provided the material used came from a rabid animal. 



Course and Prognosis. — ^The disease usually lasts four to 

 seven days. It is extremely rare for it to exceed ten days in 

 any animal. While a few recoveries have occurred in cases 

 produced by artificial inoculation, authentic records of 

 recovery from natural infection are wanting. The disease is 

 generally fatal. 



Treatment. — Once the disease is fully developed no treat- 

 ment is of any avail. To prevent rabies the fresh bitten 

 wound should be thoroughly disinfected with a 3 per cent, 

 carbolic acid or a 1 per cent, bichlorid of mercury solution. 

 If the wound is older and granulating the actual cautery or 

 caustics, such as strong hydrochloric acid, sulphuric acid, 

 strong ammonia, etc., are indicated. Subcutaneous injec- 



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