GROWTH OF BACTERIA IN PROTEIN-FREE PRODUCTS 219 



The meningococcus cultures were kept at 18°, the others in the 

 refrigerator, and subcultures were made on the control medium 

 at various intervals. After seven days all were still alive, but 

 after seventeen days pneumococcus no. 80 had died on both 

 media and pneumococcus no. 690 on the opsine. At twenty- 

 five days, pneumococcus no. 690 was still alive on the control 

 medium, but gonococcus no. 287 had died on both media and 

 M. catarrhalis on the opsine. At the end of one month pneumo- 

 coccus no. 690 and M. catarrhalis had died on the control also. 



In another lot kept at 16° for twenty-eight days, pneumococ- 

 cus no. 80 was still alive on both media, pneumococcus no. 690 on 

 opsine, but not on the control, gonococcus no. 287 on the con- 

 trol but not on the opsine, M. catarrhalis on neither, and the 

 others on both. 



On decolorized opsine the growth and viability of these organ- 

 isms was distinctly less than on the undecolorized medium. 



Acid-digestion products as culture media 



Casein, milk albumin and edestin were the proteins chosen for 

 the preparation of the digestion products. Casein contains all 

 of the well-known amino acids with the exception of glycocoU and 

 possibly cystine. In its crude form it is cheap and readily 

 obtainable. Commercial milk albumin also is inexpensive, but 

 it contains a limited number of amino acids, alanine, valine, leu- 

 cine, aspartic acid, glutamic acid, phenylalanine, tyrosine, pro- 

 line and tryptophane having been found. Edestin is a represen- 

 tative of the group of vegetable proteins, and contains all of the 

 amino acids save perhaps oxyproline. 



The above proteins were hydrolyzed with hydrochloric acid 

 and the products prepared for us by Professor Lafayette B. 

 Mendel, as follows. 



Casein product A. One hundred grams of casein were heated with 

 400 cc. of concentrated HCl for a few hours on the water bath, under a 

 reflux condenser. There was much charring, so the mixture was 

 diluted with 150 cc. of water and heated over a free flame for eight 

 hours. A large amount of humus residue was filtered off. The filtrate 



