480 BACTERIOLOGY. 



teria having the morphology of the one we are seek- 

 ing, and as soon as such is detected gelatin plates 

 and cultures in peptone solution (for the indol reac- 

 tion) should be made. The peptone culture from the 

 original material should be examined microscopically 

 from hour to hour after the sixth hour that it has 

 been in the incubator. The material taken for ex- 

 amination should always come from near the surface 

 of the fluid, and care should be taken not to shake 

 the tube. As soon as comma bacilli are detected in 

 considerable numbers in the upper layers of the 

 fluid agar-agar plates and fresh peptone cultures 

 should be made from them. In from ten to twelve 

 hours at 37 C. the colonies will develop on the agar- 

 agar plates to a size sufficient for recognition by micro- 

 scopic examination, and from this examination an 

 opinion can usually be formed. This opinion should 

 always be controlled by cultures in the peptone solution 

 made from each of several single colonies, and finally 

 the test for the presence or absence of indol in these 

 cultures should be made. 



In all doubtful cases, in which only a few curved 

 bacilli are present, or in which irregularities in either 

 the rate or mode of their development occur, pure cult- 

 ures should be obtained as soon as possible by the agar- 

 agar plate method and by the method of cultivation in 

 peptone solution, and their virulence tested upon ani- 

 mals. For this purpose cultures upon agar-agar from 

 single colonies must be made. From the surface of 

 one of such cultures a large wire-loopful should be 

 scraped and broken up in about one cubic centimetre 

 of physiological salt solution, and the suspension thus 

 made injected by means of a hypodermic syringe directly 



