i6 



Scientific Proceedings (117). 



the amount of one vitamine did not have any effect, the addition 

 of the missing component in both of the above cases caused a 

 prompt resumption of growth. The rats given both B and D from 

 the start together with the last filtrate, which contains neither B 

 nor D, showed a normal behavior both in regard to growth and 

 appearance. The influence of the last filtrate does not seem to 

 be very important but has to be investigated. 



The results suggest that the rats and possibly other mammals 

 require, besides the vitamine A, at least two vitamines of the B 

 type, namely the B and D vitamine, for their well-being and 

 growth. 



8 (1755) 



Comparative buffering value of American peptones. 



By J. BRONFENBRENNER, G. G. DE BORD and P. F. ORR. 



[From the Department of Preventive Medicine and Hygiene, Harvard 

 Medical School, Boston, Mass.] 



Some time ago one of us 1 reported before this Society the 

 results of the inquiry into the effect of the composition of the 

 medium as affecting the reliability of the cultural methods of 

 identification of bacteria, and has particularly insisted on the 

 role of the buffer and on necessity of quantitative adjustment of 

 media in respect to its buffer content. 



In the present investigation we have attempted to determine 

 the buffer content of a few of the commercial peptones with the 

 view of determining the limits of possible variation in the buffer 

 content in the media prepared in different laboratories as due to 

 the choice of peptone alone. The method used was that of de- 

 termining electrometrically the hydrogen ion concentration of the 

 various peptone solutions before and after the addition to them 

 of measured amounts of acid and alkali respectively. The study 

 demonstrated the fact that initial reaction of different peptones 

 varies within fairly broad limits, that due to complexity of com- 

 position the buffering action of any given peptone varies at dif- 

 ferent zones of hydrogen ion concentration, and that buffering 

 action of one peptone at a given hydrogen ion concentration may 



1 Bronfcnbrenner and Schlesinger, Proc. Soc. Exp. Biol, and Med., 1918, 

 xvi , 44. 



