562 



WILLIAM S. STURGES AND LEO F. RETTGER 



was SO small in these suspensions that the total gas volume seldom 

 reached 1 cc, and hence considerable error may have been 

 introduced into the determination, although all of the tests were 

 run in duplicate. 



In the following experiments on Bad. coli suspensions the 

 biuret method was somewhat modified so as to make it more 

 delicate. Instead of the 0.25 per cent basal solutions of Witte's 

 peptone, 0.1 per cent strengths were employed, which furnished 

 standards with 0.1 mgm. intervals, each interval being repre- 

 sented on the ordinate by 0.01. 



0.0 



BIURET 



'^^l_ 



© 



5- /O /S 20 ^S 30 JS 

 TIM€ IN DATS 



Chart 4. Bad. coli 



AMIN0-NITR06EN 



/S 30 £S .30 3S 



Tinc IN OAYS 







f f^ 



^ ELECTRICfd. CONDUCTIVITY 



CAPfXSSEO IN fKCIPmCAL OMfH 



S 10 IS iC !: 



TiMC IN curs 

 Chart 5. Bact. coli 



Charts 4 and 5, barring curve Via, show only a sUght decrease 

 in biuret and a corresponding increase in amino nitrogen. The 

 biuret change in Via was far greater than in any of the others, 

 and is suggestive of action by enzjTiies other than those of Bact. 

 coli, that is the presence of contaminating bacteria. It was 

 impossible to demonstrate any contamination, though it may 

 have existed, owing to the toluol which was added as an anti- 

 septic, and to the inconclusive results of microscopic study. 



Curves Vlb and Vic represent control suspensions which were 

 heated to 60° and 75°, respectively, for thirty minutes, before 



