16 L. F. RETTGER, N. BERMAN AND W. S. STURGES 



introducing only a small number of the bacteria and as little 

 extraneous matter as possible. The fate of the bacteria and of 

 the proteins was determined in three ways; first, by the plate 

 method of determining the numbers of cultivable bacteria at the 

 beginning of the experiments and after varying intervals or 

 periods of incubation ; second, by noting any change in the appear- 

 ance of the media; and finally by determining the amount of 

 coagulable protein at different times, during the course of the 

 experiments. 



The results obtained by Sperry and Rettger (1915) were so 

 definite and consistent as to leave no doubt as to their signifi- 

 cance. It was assumed that the purified proteins resisted decom- 

 position by direct bacterial action because of their original or 

 imchanged condition as native proteins; hence, sterilization by 

 heat was to be avoided, as heating at coagulation temperature 

 undoubtedly causes changes in the protein molecule. 



The present investigation is in part a continuation of the work 

 of Sperry and Rettger on the action of bacteria on purified 

 proteins. Instead, however, of studying the behavior of bacteria 

 toward unchanged (unheated) proteins, the experiments were 

 conducted on test media containing coagulated egg albumin as 

 the only possible source of nitrogen. The investigation also in- 

 cluded a study of the behavior of bacteria toward proteoses 

 and peptones, and of so-called "bacterial autolysis." 



I. THE BEHAVIOR OF BACTERIA TOWARD PURIFIED COAGULATED 



EGG ALBUMIN 



The egg albumin was prepared by the method of Hopkins and 

 Pinkus (1899). The test medium containing the albumin and 

 inorganic salts was the same as that used by Bainbridge and by 

 Sperry and Rettger, with the exception that the medium was 

 sterilized by heat and hence contained coagulated albumin. The 

 methods of inoculation, incubation and determination of results 

 were the same as those described in the earher paper from this 

 laboratory, (Sperry and Rettger, 1915). Special attention was 

 given to the enumeration of bacteria by the usual plate method 



