368 NATHAN BERMAN AND LEO F. RETTGER 



peptone, and even after four weeks of incubation the decrease 

 was small, with one exception. 



The work upon which this paper is based was a continuation 

 of the investigations to which reference has been made, and dealt 

 with the following topics: 



a. The behavior of bacteria towards coagulated egg albumin. 



b. The utilization of different brands of commercial peptone. 



c. The utilization of ''purified" proteose. 



d. The utilization of gelatin and casein. 



e. The utilization of the products of Witte's peptone and of 

 casein obtained by partial digestion with trypsin. 



THE BEHAVIOR OF BACTERIA TOWARDS COAGULATED EGG ALBUMIN 



The results obtained were in strict accord with those of the 

 earlier experiments. A number of additional organisms were 

 employed in the later tests, as for example Pseudomonas fluo- 

 rescens, Bacillus cloacae and new strains of Proteus vulgaris, 

 Bacillus subtilis and Bacillus coli. 



But one conclusion can be drawn from the results of the com- 

 bined tests. Coagulated egg albumin, like the unheated and 

 unchanged proteins previously studied, resists the action of 

 even the most active proteolytic bacteria, and can be utilized as 

 food only after at least partial disintegration or cleavage by 

 enzymes or other protein-destroying agents. In all of these 

 experiments the methods employed were the same as those 

 described by Sperry and Rettger (1915). 



The individual cell, whether animal, plant or bacterial, re- 

 quires simple forms of nitrogen, at least until it may produce its 

 own enzjrmatic substance. The nourishment of bacteria is, as 

 Distaso (1916) has well stated, a passive one, and depends upon 

 substances which can readily pass through the cell walls and be 

 absorbed by the protoplasm. This view is further supported by 

 the experiments which follow. 



