212 



HAROLD C. ROBINSON AND LEO F. RETTGER 



This system was employed in all of the experiments. In 

 estimating the growth of any particular organism a mental 

 comparison was made with the average growth of that organism 

 on the corresponding extract-peptone medium. This standard 

 growth was rated as + + +. These comparisons are, of course, 

 only roughly approximate. Special care was taken, however, 

 to make the inoculations light and as nearly alike as possible. 

 In duplicate experiments the growths agreed surprisingly well. 

 Only a few of the tables are presented in this paper. For a com- 

 plete record the reader is referred to the original thesis in the 

 Yale Library. 



In the following experiments the media had the same composi- 

 tion as those employed by Dalimier and Lancereaux. 



Medium I 



Opsine 1.0 per cent\ faintly acid to 

 NaCl 0.5 per cent / litmus 



Medium II 

 Opsine 1.0 per cent 

 NaCl 0.5 per cent 

 Glycerol 5.0 per cent 



faintly acid to 

 litmus 



Medium III 

 Opsine 1.0 per cent 1 faintly alkaline 

 NaCl 0.5 per cent / to litmus 



Medium IV 

 Opsine 1.0 per cent 

 NaCl 0.5 per cent 

 Glycerol 5.0 per cent 



faintly alkaline 

 to litmus 



Each of the media was employed with and without agar, the 

 amount of agar in the solid media being 1.5 per cent. As test 

 organisms 12 of the common and representative pathogens, and 

 5 non-pathogens were used. The following is a summary of the 

 results. 



The alkaline was the more favorable of the two reactions for 

 M. cholerae, B. anthracis, B. abortus, Sir. pyogenes and the 

 diphtheria group, and the acid for B. pyocyaneus, Staph, aureus 

 and B. typhi. On the opsine agar the growths were much better 

 than in the opsine bouillon, being in general almost equal to 

 those on the common meat extract peptone agar, and slightly 

 better than those on a medium of Witte's peptone 1 per cent., 

 NaCl 0.5 per cent, agar 1.5 per cent. Glycerol in the alkaline 



