EXAMINATION OF CULTURES lit) 



to liquefy gelatin, by continued cultivation, cultures must be 

 kept under observation for a considerable time. For ex- 

 ample, B. suipestifer produces no change in the appearance 

 of milk for at least two weeks after which it begins to 

 saponify. This very distinctive character can not be de- 

 termined in a few days. Again, the composition of the cul- 

 ture medium may be such as to modify the appearance of the 

 growth. In identifying species or describing new ones great 

 care should be exercised in accurately determining the cul- 

 tural characters and pathogenesis of the organisms. 



