ACIDURIC BACILLI 



195 



as acid forming and coagulating, acid forming, inert, alkali 

 forming, and peptonising. A comparison of the milk tube 

 method arid the litmus lactose gelatine plates was made by 

 Ayers and Johnson 8 who obtained the following results as the 

 averages of four samples. 



The milk tube method possesses the advantage of differen- 

 tiating those organisms having feeble fermentative ability and 

 also develops a larger proportion of peptonisers. The latter 

 result may be partially due to the nature of the nitrogenous 

 substance used for the test as it is exceedingly improbable 

 that proteolysis proceeds at the same rate with all test sub- 

 stances. 



Aciduric Bacilli. Among the acid-producing organisms, 

 one sub-division, that of the aciduric or acidophylic bacteria, 

 is especially worthy of further mention because it contains the 

 commercially important B. bulgaricus. This organism has 

 achieved considerable repute during the last few years as a 

 therapeutic agent by reason of its influence on the flora of the 

 intestinal canal and it has, consequently, become necessary 

 to make bacteriological examinations of the tablets used for 

 this purpose. 



Although the aciduric bacilli grow luxuriantly in dextrose 

 and lactose broth containing acetic or lactic acid they usually 

 grow very sparingly or not at all on the usual laboratory media. 

 They vary considerably in length (3 to 7 M) and occur singly or in 

 chains or threads. They develop under both aerobic and anaer- 

 obic conditions and, although typically Gram positive, old cul- 



