UTILIZATION OF PROTEID AND NON-PROTEID NITROGEN 31 



proteins could be observed if the flasks had been inoculated with 

 members of the colon-typhoid group or with other gelatin-non- 

 liquefying bacteria. On the other hand, organisms which are 

 known to elaborate proteolytic enzymes, as for example B. 

 prodigiosus and B. subtilis, rapidly brought about destruction of 

 the proteins. Te^t media containing purified coagulated egg 

 albumin or dialyzed proteoses as the only possible source of 

 available nitrogen were, with few exceptions, not attacked, how- 

 ever, even by the gelatin-liquefyers, if the inoculations were 

 made with but comparatively few organisms and from a culture 

 less than twenty-four hours old. 



The slight reduction in the amount of "peptone" which was 

 observed in a few instances may have been due to agents other 

 than enzymes or bacterial cells, as for instance acids and am- 

 monia. It is significant that such reductions did not become 

 apparent until at least two to three weeks after the time of 

 inoculation. These slight losses in the soluble proteins, if they 

 were losses, usually occurred in flasks containing luxurious 

 growths, and may possibly be due to adsorption by the bacteria 

 and other suspended matter and by the w^alls of the flasks which 

 were more or less coated. The possibility of the occurrence of 

 small amounts of a proteolytic enzyme having the properties of 

 erepsin (Cohnheim, 1901, Vernon, 1904) cannot be ignored. 

 However, if such an enzyme is produced by organisms of the 

 B. coll and B. typhi type it is of little importance, as no indi- 

 cations of any proteolytic action whatever were apparent during 

 the first two weeks, and since only very minute quantities can 

 be produced even under the most favorable cultural conditions. 



The statement that purified albumin and dialyzed proteoses 

 were not attacked even by gelatin-liquefying bacteria if the test 

 fluids were inoculated with few organisms taken from very young 

 cultures may appear at first paradoxical. The results, which 

 are in harmony with those of Bainbridge and the earlier investi- 

 gations in this laboratory on purified albumins, readily admit of 

 an explanation. When the test medium contains no other possi- 

 ble source of nitrogen for cell metabohsm besides the purified 

 protein it is not attacked by any bacteria unless a sufficient 



