INOCULA TION OF ANIMALS. 1 1 1 



knowledge is attained regarding the bacterium, which will 

 lead to its identification. In the case of many well-known 

 organisms, however, a few of the above points taken together 

 will often be sufficient for the recognition of the species, and 

 experience teaches what are the essential points as regards 

 any individual organism. In the course of the systematic 

 description of the pathogenic organisms, it will be found 

 that all the above points will be referred to, though not in 

 every case. 



INOCULATION OF ANIMALS. 1 



The animals generally chosen for inoculation are the 

 mouse, the rat, the guinea-pig, the rabbit, and the pigeon. 

 Great caution must be shown in drawing conclusions from 

 isolated experiments on rabbits, as these animals often 

 manifest exceptional symptoms, and are very easily killed. 

 Dogs are, as a rule, rather insusceptible to microbic disease, 

 and the larger animals are too expensive for ordinary 

 laboratory purposes. In the case of the mouse and rat the 

 variety must be carefully noted, as there are differences in 

 susceptibility between the w^ild and tame varieties and the 

 white and brown varieties of the latter. In the case of the 

 wild varieties, these must be kept in the laboratory for 

 a week or two before use, as in captivity they are apt to die 

 from very slight causes, and, further, each individual should 

 be kept in a separate cage, as they show great tendencies to 

 cannibalism. Of all the ordinary animals the most suscep- 

 tible to microbic disease is the guinea-pig. Practically all 

 inoculations are performed by means of the hypodermic 

 syringe. The best variety is made on the ordinary model 

 with metal mountings, asbestos washers, and preferably 

 furnished with platinum iridium needles. Before use the 

 needle is mounted on the piston and sterilised by boiling 

 for five minutes. The materials used for inoculation are 

 cultures, animal exudations, or the juice of organs. If the 



1 Experiments on animals, of course, cannot be performed in this 

 country without a license granted by the Home Secretary. 



