484 



LEWIS DAVIS 



article on hydrogen ion concentration determinations mentioned 

 above (Davis, 1918) shows these changes with a toxicogenic strain. 



It is further shown in the same publication that the final hy- 

 drogen ion concentration of high strength toxin L + dose less than 

 0.25 cc.) after two weeks incubation ranged from C H = 1.6 X 

 10- 8 (pH = 7.79) to C H = 5.2 X 10~ 9 (pH+ = 8.28). At the same 

 time, low strength toxins were obtained, the final H ion concentra- 

 tion of which came within the above limits. It is obvious from 

 the table that in the normal development of Corynebact. diphtherial 

 in bouillon, the organisms may produce the same H ion concen- 

 tration at two different intervals which represent wide variations 

 in potency. This fact, and what has been stated above, justify 

 the conclusion that there is no direct relationship, during or after 

 growth, between the H ion concentration of the medium and 

 production of toxin. 



d. Final operations 



The contents of the large toxin flasks, after proper incubation, 

 are checked microscopically to determine purity of culture; 0.4 

 per cent of purified cresols is then added and allowed to act for, 

 at least, twenty-four hours to ensure thorough germicidal action. 

 As a rule, filtration can be accomplished satisfactorily through 

 paper, otherwise Mandler filters may be employed. During 



