XI, B, 4 



Wade: Carbohydrate Fermentation 



175 



Two sets of agar slants, maltose and glycerin, were cultivated 

 in vacuo at body temperature in a Novy jar. The reactions 

 were at first accelerated to equal those of the room-temperature 

 control cultures, but at the end of a week the cultures showed 

 little difference from the aerobic incubator controls. Later du- 

 plicate sets of 1 per cent maltose serum-water and litmus agar 

 were similarly cultivated. Here there was definitely, although 

 but slightly, more active fermentation in the anaerobic sets, the 

 advantage persisting through the four days for which the cul- 

 tures were observed. 



FERMENTATION IN HISS'S LITMUS SERUM-WATER 



Effect on medium of directly added acids. — Comparison of the 

 reactions of B. pestis in serum-water cultures and on litmus agars 

 is distinctly unfavorable to the former, though it would seem 

 that, so far as the indicator is concerned, the results should coin- 

 cide. The possibility that a so-called "buffer" absorption of acid 

 by the serum itself might play some part in the delayed reaction 

 was considered. To determine this, increasing amounts of dilute 

 hydrochloric and lactic acids were slowly added to measured 

 volumes of sugar serum-waters, the tubes being agitated the 

 while. The results were practically identical in several tests. 

 The amounts of acids required to produce the changes are small 

 and regular, and the "buffer" effect is, at the most, but 0.1 to 

 0.2 per cent. The acidity required to produce various stages 

 represented heretofore by the "plus system" is shown in Table 

 IX. By the application of these equivalents, the readings in 

 Tables I and VIII might be made roughly quantitative. 



Table IX. — Changes produced by adding dilute acids to Hiss's litmus serum- 

 water, as determined with hydrochloric and lactic acids. 



Normal 

 acid. 



Per cent. 

 0.1 

 0.2 

 0.3 

 0.4 



Appearance with transmitted light. 



None, or faintest perceptible change .. 



Slight reddening 



Red predominant --- 



Red almost pure 



0.5 I (About as above) faintest clouding .. 

 0.6 ilRed practically pure; opacity devel- 



0.7 

 0.8 



0.9 

 1.0 



opmg. 

 Red and opaque, but fluid . 



Coagulated . 



Appearance with reflected light. 



No change 



No change ._. 



Faint reddening.. 



Reddening more distinct 



(About as above) 



Red and blue about equal; precipita- 

 tion not detectable. 



Red practically pure; opacity evi- 

 dent. 



Coagulated 



Equiva- 

 lent to 

 symbols 

 as used. 



+ 

 2+ 



3+ 



4-t- 



