114 LABORATORY BACTERIOLOGY 
II 
ANIMAL INOCULATION FOR PURPOSES OF DIAGNOSIS 
It is not always possible by the ordinary culture methods to 
determine the specific nature of a disease from a small piece 
of affected organ or tissue of the diseased animal. To make a 
positive diagnosis, therefore, it is often necessary to resort to 
animal inoculation. This is done by injecting into the animal 
chosen a small quantity of the tissue or fluid supposed to 
contain the virus of the specific disease, such as tuberculosis, 
glanders, rabies, and others. Animal inoculation is further de- 
mandatory in determining the degree of virulence of patho- 
genic bacteria, or the strength of toxins, antitoxins, etc. In other 
words, the living animal must for the present serve in certain 
instances as a testing reagent. The fact should be kept in mind 
that the lesions produced in the experimental animal are not 
necessarily the same, and in most cases are not the same, as those 
in the animal from which the virus was obtained. It is the rule, 
however, that each virus produces characteristic lesions from 
which the disease can usually be diagnosed in the smaller animal. 
Animals used. For simple diagnostic work the guinea pig 
and rabbit are usually employed, although white and gray mice, 
dogs, and other animals are sometimes used. 
Method. In preparing the animal for inoculation the hair 
should be removed over the area of operation by the use of 
scissors, and the skin washed and disinfected. A solution of 
corrosive sublimate, 1 to 1000, or a 5% solution of carbolic 
acid, may be used. The incision should be made with a sharp 
knife. Liquid material is injected with a hypodermic syringe. 
An anesthetic should be given whenever the pain inflicted is 
to be long continued or excessively severe. The place of in- 
oculation should be chosen where a local swelling would not 
interfere with the animal’s locomotion. 
