ANTISEPTIC SURGERY 173 



ditions unfavorable for its life presented difficulties 

 owing to the formation of spores, but Pasteur 

 found, after considerable experimenting, that if it 

 were grown in neutral chicken bouillon at 4 2- 43° C. 

 the spores would not develop. A month of this 

 regime usually suffices to kill the bacilli; they be- 

 come weaker and weaker apparently, and after ten 

 or twelve days they may be injected into rabbits, 

 guinea pigs, and sheep without producing fatal re- 

 sults. If the weakened bacteria were grown at 

 35° C, thus allowing them to form spores, the 

 bacteria subsequently emerging from these spores 

 were found to produce the same mild effects as the 

 bacteria from which they were derived. This is a 

 fortunate circumstance, as it enables one to pre- 

 serve the attenuated virus in a relatively permanent 

 form. Pasteur found, as in chicken cholera, that 

 the inoculation of animals with attenuated virus 

 would produce mild effects which would render the 

 animals immune to inoculation with the unmodified 

 bacilli of this disease. After making sure of the 

 success of his vaccine he announced his discovery 

 to the Academy of Sciences. "I could not be con- 

 soled," he remarked to his family, "if this dis- 

 covery which my collaborators and I have made 

 had not been a French discovery." 



