184 PRODUCTION OF CARBON DIOXIDE 



of an equivalent amount of NaOH to the medium produced com- 

 plete recovery, as shown by the production of CO^. No recovery was 

 obtained by washing, centrifugalizing, and rewashing the organisms 

 in dextrose solution without the addition of NaOH. When a greater 

 amount of acid was added, the addition of NaOH produced only 

 partial recovery. When the medium was made extremely acid, no 

 recovery took place. 



Recovery from the effects of the addition of alkali to these or- 

 ganisms was spontaneous, varying in the time required for recovery 

 according to the amount of alkali added. When an equivalent 

 amount of acid was added recovery was hastened. 



In short, decreases in the rate of CO2 production caused by the 

 addition of acid to these organisms were irreversible or only par- 

 tially reversible (except in certain cases in which slight additions of 

 acid were neutralized by a subsequent addition of alkali) while de- 

 creases of similar magnitude caused by the addition of alkali, were 

 spontaneously reversible. These results are essentially similar to 

 those obtained by Gustafson^ in his recovery experiments with 

 Penicillip.m. 



It is evident that the effects of NaOH are not to be ascribed, to 

 any measurable extent, to the action of Na, since previous experi- 

 ments^ have shown that when NaCl is added to Bacillus suUilis 

 there is a decrease in the CO2 production only when the total con- 

 centration of NaCl is greater than 0.15 m. In all of the above experi- 

 ments the concentration of NaOH used was considerably less than 

 this (about one- tenth as great). 



It may be objected that the observed decrease in the carbon dioxide 

 production caused by the addition of NaOH is in reahty due to 

 buffer action or to the formation of carbonates and bicarbonates as 

 a result of the neutralization by NaOH of the CO2 produced by the 

 bacteria. In view of the fact that the greatest amount of alkali 

 added in any experiment was one drop of 0.1 n NaOH it did not 

 seem probable that this buffer action was important. The following 

 series of experiments shows that it is negligible. The normal rate 

 of production of CO2 by 2 cc. of an emulsion of living bacteria was 

 determined. A tube containing 2 cc. of distilled water was then 

 inserted into the system so that the CO2 coming from the bacteria 



