1922] 



ROSEN — A BACTERIAL DISEASE OF FOXTAIL 



367 



TABLE V 



CHANGE IN Ph OF ACID BROTHS AFTER STANDING 10 DAYS UNINOCU 



LATED 



Acids 



Original Ph 



Final Ph 



Acetic 



4.9 



4.8 



5.3 



4.8 



Citric 



5.0 

 4.8 



5.3 

 5.0 



Hydrochloric 



4.5 



5.0 



Lactic 



4.8 



5.0 



Malic 



4.7 



5.0 



Phosphoric 



4.9 

 4.3 



5.2 



4.8 



Tartaric 



4.9 

 4.5 



5.3 



4.6 



For example, citric acid broth changed from Ph 4.8 to Ph 5.0, an 

 hydrogen-ion concentration not sufficient to prevent growth (see 

 table in), yet when citric acid broth testing P H 5.0, originally 

 Ph 4.8, is inoculated there is no growth. The same is true for 

 lactic, malic, and tartaric acids. Without more experimental data 

 it is not possible to give an acceptable explanation of the change, 

 which in this whole series is toward the alkaline side. There is 

 of course some possibility that even with Jena glass there is a 

 slight amount of alkali produced, particularly in strongly acid 

 media; other possibilities such as the production of compounds in 

 which a greater proportion of OH ions is set free may also be 

 considered. 



To test further the effect of the anion of various acids, 0.5 

 cc. of 0.405 N sodium hydroxide was added aseptically to 20 cc. 

 of such acid media as had previously given no growth. (The al- 

 kali had first been sterilized so that there was no need of auto- 

 claving after it had been added.) The results are shown in table 



VI. 



Table vi, in comparison with table in, brings out very 

 sharply the poisonous effect of the acetate anions when the hydro- 

 gen ions are not the limiting factors. However, it would appear, 

 judging by the results of the phosphoric acid tests, that there 

 may be limiting factors other than the cation and the anion. For 

 one thing, it is hard to believe that the phosphate radicle, as such, 



