372 



NATHAN BERMAN AND LEO F. RETTGER 



diminution in these substances. Most of the gelatin liquefiers 

 were able to utiHze the proteins completely within a period of 

 three weeks. B. subtilis, B. cereus, B. prodigiosus and Proteus 

 vulgaris were especially active in this respect. On the other 

 hand, the non-liquefiers exerted but a weak peptolytic action, 

 the average amount of biuret-giving substances acted upon 

 being less than 30 per cent of the total. Among the gelatin 



TABLE 2 

 Weekly tests showing utilization of Witte's peptone 



ORGANISMS 



BltTRET TEST 



1 week 2 weeks 3 weeks 4 weeks 



SORENSEN TEST 



1 week 2 weeks 3 weeks 4 weeks 



(1) Without beef extract 



Control 



B. subtilis 



Staph, aureus. 



B. cloacae 



B. typhi 



B. coli, average 2 strains. 



16.0 

 90.0 

 46.0 

 52.0 

 32.0 

 52.0 



Medium: 1 per cent peptone, and 0.5 per cent NaCl. 

 (2) With beef extract 



Control 



B. subtilis 



Staph, aureus 



B. cloacae 



B. typhi 



B. coli, average 2 strains. 



24.0 

 112.0 

 76.0 

 78.0 

 48.0 

 54.0 



Medium: 1 per cent peptone, 0.25 per cent Liebig's beef extract and 0.5 per cent 

 NaCl. 



liquefiers Staphylococcus aureus and St. alhus and B. cloacae 

 also were comparatively weak. 



Table 3 shows that different salts used in medium B do not 

 affect the course of decomposition of the peptone, as compared 

 with the plain nutrient broth. 



The small decrease in the biuret-giving substances during the 

 first week of incubation, brought about by the gelatin liquefiers. 



