COHN, WOLBACH, HENDERSON, AND CATHCART 22." 



Preparation of the Media. 



Cohn's Medium with the Addition of Asparagine. 



K2HPO4 5 . gm. 



Ca3(P04)2 0.5 " 



MgS04 5.0 " 



Ammonium tartrate 10 .0 



Asparagine 4.0 



Distilled water 1,000 .0 cc. 



The ingredients were weighed and dissolved in the water and after tubing weie 

 sterilized in the autoclave at 15 pounds pressure for 30 minutes. 



Wheat Bouillon. 



Wheat flour 15 .0 gm, 



MgS04 0.5 " 



KNO3 1.0 " 



Dextrose 15.0 



Distilled water 1,000.0 cc. 



The wheat flour was added after solution of the other ingredients and the 

 whole boiled for a few minutes, tubed, and sterilized in the autoclave at 15 

 pounds pressure for 30 minutes. 



Potato Broth. — Two parts of water to one of freshly grated raw potatoes were 

 mixed and allowed to stand for 24 hours. The mixture was then strained through 

 cloth and the liquid filtered through coarse filter paper, tubed, and sterilized at 

 15 pounds pressure for 30 minutes. It was not considered of importance to 

 avoid the precipitate which occurred. 



The cultures were incubated for 5 days; meanwhile they were ob- 

 served daily, and finally both inoculated tubes and controls were 

 examined for their hydrogen ion concentrations. The results of this 

 experiment are presented in Table I. It should be noted that the re- 

 sults with the wheat paste were uncertain. This appears to be due 

 to its lack of homogeneity, and low buffer content. It is also to be 

 observed that the spores are, as might be expected, somewhat more 

 restricted in growth than the organisms themselves. 



A second experiment was performed over a narrower range of hy- 

 drogen ion concentration, the results of which, presented in Table II, 

 agree satisfactorily with those of the first experiment. 



From these experiments it seems safe to conclude that a hydrogen 

 ion concentration sensibly higher than 10~ N completely inhibits the 

 growth of Bacillus mesentericus . 



