Optimum Concentration for Growth of B. typhosus. 151 



lesions will take place fifteen to twenty-five years later as in the 

 case of extensive thermal burns. Finally, the psychical disturb- 

 ances following mustard gassing should not be minimized. 



As to its use in warfare, mustard gas is a disabling rather 

 than a killing agent. Under the actual conditions of the field 

 the great majority of mustard gas casualties are likely to be of a 

 nature tending to incapacitate the injured for service for a number 

 of days or weeks, or even for months. Added to this, the in- 

 sidious character of this invisible fire, painless and often unrecog- 

 nized in its action, makes mustard gas a potent factor in under- 

 mining the morale of the troops exposed to it. 



Abstracts of the Communications, Pacific 

 Coast Branch. 



Twenty-second meeting. 



Berkeley, California, May 15, igig. 



84 (1459) 



The optimum H-ion concentration for the growth of B. typhosus, 

 and the effect of changes in H-ion concentration on 

 the generation time. 



By P. Schoenholz and K. F. Meyer. 



[From the George Williams Hooper Foundation for Medical Research, 

 University of California Medical School, San Francisco.] 



1. B. typhosus has a range of growth from P H + 5.0 — P H + 8.6, 

 with an optimum growth at P H + 6.8 — P H + 7.0. 



2. Stock cultures isolated from stools, blood, and urine have a 

 more decided optimum than recently isolated cultures. In such 

 cultures, the plateau is much more pronounced and extends over a 

 wider range than in stock cultures. The latter is suggestive of 

 microbic adaptation to changes in H-ion concentration in body 

 fluids, particularly urine and bile. 



3. The growth curve is influenced by changes in H-ion con- 

 centration. 



