202 Manual of Veterinary Microbiology. 



vaccinates the organism against more active virus. 

 The French authors recommend the successive em- 

 ployment of two vaccines, one exposed to 100° 

 the other to 90°, during seven hours. These two 

 vaccines are dry when taken from the oven in 

 which they have been prepared ; the dose employed 

 is one centigram of the powder diluted in a gram of 

 water for each animal. The vaccine prepared at 100° 

 is first used, and then, after eight days, the other. 

 The inoculations are made in the cellular tissue of the 

 ear, or in the internal face of the end of the tail. The 

 autumn or the end of winter are the seasons selected 

 for the operation. It is necessary to guard against in- 

 oculation during very hot weather as an elevated 

 temperature increases the activity of the virus. 



The consequences of the vaccinal inoculation are 

 local and general. At the inoculated point an en- 

 gorgement develops, generally of small extent and 

 healing spontaneously. At the same time there is 

 observed a febrile reaction, which indicates the exist- 

 ence of the disease in a mild form. 



Kitt recommends a single vaccine prepared at 90°. 



When the virus has been thus artificially attenuated 

 it can regain its original activity by successive pas- 

 sages through the bodies of young guinea pigs, and 

 also under the influence of lactic acid, etc., as already 

 described. 



Animals can also be vaccinated by injection of the 

 natural virus either in the cellular tissue or into the 

 blood. We have seen above, that inoculation of small 

 doses in the connective tissue confers immunity in 

 place of the disease, and that the blood tolerates com- 

 paratively large doses of the virus. Injection into 



