GROWTH OF BACTERIA IN PROTEIN-FREE PRODUCTS 221 



ference. Tyrosine and leucine crystals were detected in all of the 

 solutions, on evaporation, and glutamic acid crystals in the 

 " Lactalbumin product." Millon's test was always positive. 



It was found, by evaporating to as near dryness as possible, 

 that a medium containing 5 per cent of any of these solutions 

 consisted of about 1 per cent solid matter. Sorensen's formalin 

 titration for monamino acids was tried on the casein products. 

 5 cc. of a 5 per cent solution of "Casein A" required 4.1 cc. of 

 ^ NaOH to neutralize it after the addition of the neutral formalin. 

 With "Casein B" and "Casein C" the figures were 2.9 cc. and 

 3.7 cc. of ^ NaOH respectively. In an ammonia determination 

 by Folin's method, 10 cc. of the original "Casein C " solution was 

 found to contain 25 mgm. of N as NH3. The other solutions were 

 not tested. 



All of these products could be decolorized and made up into 

 culture media in the same easy and rapid way as opsine. Con- 

 siderable NaOH was necessary to neutralize the media. It was 

 found that 100 cc. of a 5 per cent "Casein C" solution required 

 about 0.8 cc. of j NaOH to make it neutral to litmus, so there 

 was approximately 0.5 per cent of NaCl formed in the process. 

 The other media did not differ very materially from this. 



Bacterial Growth in Casein Products 



In a medium of "Casein A" only, decolorized and of 10 per 

 cent strength, 17 saprophytes and 14 pathogens, including, 5. 

 anthracis, B. typhi, M. cholerae, Bad. pullorum, B. diphtheriae, 

 B. pseudo-diphtheriae and Streptococcus, were grown; also two 

 streptothrices and two moulds. When the reaction was neutral 

 to phenolphthalein the diphtheria group grew sparsely, while 

 with a reaction of + 1 there was no growth. B. anthracis and M. 

 cholerae also grew better on the neutral media, while Streptococcus 

 showed the reverse tendency. Almost all of the other organisms 

 grew quite well on both media. Color production was weak or 

 entirely lacking with B. prodigiosus. Staph, aureus, B. ruber 

 (Balticus) and S. aurantiaca, but good with B. pyocyaneus and 

 B. fiuorescens (non-liquefaciens). 



