LOUIS FREEDMAN 19 



substance was filtered off and the filtrate evaporated to dry- 

 ness in vacuum. The residue was taken up in water and the 

 solution again evaporated to dryness. This operation was re- 

 peated twice, making four evaporations, to remove the bulk of 

 hydrochloric acid. The remaining acid was then neutralized by 

 addition of normal sodium hydroxide ; the solution was made up 

 to a volume corresponding to a 10% solution of the protein, ad- 

 justed to a PH of about 7.3 and sterilized at ten pounds pressure 

 for ten minutes. 



EFFECT OF THE PROTEIN HYDROLYSATES ON THE 

 GROWTH OF STREPTOCOCCI. 



The procedure for testing the effect of the hydrolysates on 

 bacterial growth was the same as described in our previous 

 paper 5 . One c.c. of the hydrolysate was added to the sterile 

 D.I.-G.S. medium and the whole, after suitable inoculation, incu- 

 bated at 37 C. for 24 hours. Of the animal proteins tested, only 

 two, casein and commercial gelatin, gave a definite positive stimu- 

 lation to the growth of streptococci, while fibrin and lactalbumin 

 gave only a slight activity. Sulphuric acid hydrolysates of casein 

 were also strongly active. Of the hydrolysates of the proteins of 

 vegetable origin, we found only two to support the growth of 

 streptococci, namely, edestin and yeast protein. 



TABLE I. 



Effect of Protein Hydrolysates on Growth of 

 Streptococci and Yeast. 



Net yeast Bac- 



N O- Hydrolysates of Animal Proteins. 1 cc. used. growth in terial 



mm. growth 



1. Casein (Purified) HC1 hydrolysate 1.0 -f 



2. " " H 8 SO " + 



3. " (Technical) HC1 1.0 + 



4. Lactalbumin 0.6 



5. Fibrin 



6. Serum globulin 



7. Serum albumin 



8. Beef -heart (muscle) protein 



9. Egg globulin 



10. Egg albumin 



