484 APPLICATION OF METHODS OF BACTERIOLOGY 



Bouillon. It causes uniform clouding of the bouillon and 

 brings about a slightly acid reaction. 



Indol Formation. It is customary to regard this organism 

 as devoid of the power to form indol; in fact, this has hitherto 

 been considered one of its important differential peculi- 

 arities, and by the usual methods of cultivation and test- 

 ing the indol reaction is not observed in cultures. It has 

 been shown, however, by Peckham, that by repeated 

 transplantation, at short intervals, into either Dunham's 

 peptone solution, or, preferably, a freshly prepared alkali- 

 tryptone solution, made from tryptonized beef-muscle, that 

 the indol-producing function may be induced in the genuine 

 typhoid bacillus obtained directly from the spleens of 

 typhoid cadavers. 1 



It does not produce gaseous fermentation. On lactose- 

 litmus-agar-agar it grows as pale-blue colonies, causing no 

 reddening of the surrounding medium; though if glucose 

 be substituted for lactose, both the colonies and the sur- 

 rounding medium may become red. In the fermentation- 

 tube, in glucose or lactose bouillon, no evolution of gas 

 as a result of fermentation occurs. 



It grows at any temperature between 20 and 38 C., 

 though more favorably at the latter point. It is very sen- 

 sitive to high temperatures, being killed by an exposure of 

 ten minutes to 60 C., and in a much shorter time to slightly 

 higher temperatures. 



It does not liquefy gelatin. 



It grows both with and without oxygen. 



It does not grow rapidly. ' 



1 A. W. Peckham, The Influence of Environment Upon the Biological 

 Functions of the Colon Group of Bacilli, Journal of Experimental Medi- 

 cine, 1897, vol. ii. 



