202 MANUAL OF BACTER OLOGY. 



lowed by injection of pure bile or virulent blood; (3) by the 

 simultaneous injection of strong standarized serum and viru- 

 lent blood. 



In the case- of erysipelas of swine (French, rouget; German, 

 Schweinerothlauf) Pasteur secured bacilli of diminished viru- 

 lence by injecting virulent bacilli into relatively insusceptible 

 animals. The animal used was the rabbit. The bacilli were 

 passed through several rabbits in succession. Cultures taken 

 from the last of the series produced a milder form of the disease 

 and amount of immunity to a certain degree. The practical 

 value of this inoculation is not settled. 



In still another disease, black-leg of cattle or symptomatic 

 anthrax (French, charbon symptomatique; German, Rausch- 

 brand), an attenuated vims is secured by the use of heat. 

 The pulp from the infected muscle of a diseased animal, 

 containing the bacilli, is squeezed from it and heated to a 

 temperature of 95 to 99 C. for six hours. The dried material 

 mixed with water constitutes the vaccine. The Depart- 

 ment of Agriculture of the United States now furnishes this 

 vaccine free to farmers. The results of this method are said 

 to be very satisfactory.* In the human disease, bubonic plague, 

 a nearly similar procedure has been proposed by Haffkine. 

 To protect against plague, cultures of plague bacilli are used 

 which have been previously sterilized by heat, with carbolic 

 acid added as a preservative. (See section on Bubonic Plague, 

 Part IV.) In the preparation of these " vaccines" it is of the 

 utmost importance to use pure cultures, and to be sure that 

 the cultures are dead. It is not enough to subject them to 

 heating or to the action of other germicidal agents as recom- 

 mended in books, but they should in all cases be tested with 

 cultures to determine whether all the bacteria have been cer- 

 tainly killed. 



*See Annual Reports, Bureau of Animal Industry, U. S. Department of Agri- 

 culture. 



