226 HAROLD C. ROBINSON AND LEO F. RETTGER 



cent opsine were strikingly more abundant than those on Witte's 

 peptone (1 per cent). Gonococcus no. 287, smd Meningococcus 

 no. 200 grew on the opsine and not on the peptone, while the 

 reverse was true with Pneumococcus no. 697. "Casein C" 8 

 per cent and medium V, while not as good as the 2 per cent opsine, 

 were still superior to the 1 per cent Witte's peptone. Some 

 organisms grew better on one of these two and some on the other. 

 On the whole, the balance was slightly in favor of medium V. 

 Lactalbumin product paste seemed to have, in a general way, 

 about the same value as the peptone. In two successive trans- 

 plants to the same media the cultures on "Casein C" 8 per cent 

 and on medium V showed a decided tendency to die out. In the 

 case of "Casein C " 8 per cent there was no growth of the strepto- 

 cocci nor of Meningococcus no. 200. On medium V the results 

 were a little better, only two out of the five strains of streptococci 

 dying out, in addition to Meningococcus 200. On the other hand, 

 all of the cultures on the opsine medium were thriving well after 

 five transplants on this medium. 



GROWTHS IN LACTALBUMIN AND EDESTIN PRODUCTS 



A few preliminary experiments demonstrated that the edestin 

 and lactalbumin products were inferior to the casein products as 

 culture media, so little work was done with these two. On the 

 5 per cent decolorized edestin product in 1.5 per cent agar, neutral 

 to litmus, 7 pathogens and 14 saprophytes were cultivated. 

 Streptococcus, B. abortus and the diphtheria group failed to grow, 

 while the others did not thrive as well as on the casein products. 

 Pigment production by B. prodigiosus and B. ruber (balticus) 

 was especially striking and intense, and was also good with 

 Staph, aureus, M. cereus [flavus) and S. aurantiaca. In the case of 

 B. pyocyaneus the color was a deep blye, while cultures of B. 

 fluorescens were colorless, which shows that in this medium no 

 fluorescent pigment is produced, only the bluish pyocyanin. 

 When transplanted to the same medium again, B. ruber lost its 

 color, while after two or three transfers no change in the others 

 was apparent. As with the other products, the addition of 



