576 Bulletin 167 



sodium asparaginate. Upon ammonium lactate the results were 

 practically the same; however, with Ps. longa and LI, growth was 

 somewhat delayed. Ps. alba, Ps. longa, Ps. mcsenterica, Ps. 

 tenuis, XXXVI, and LI, used ammonium tartrate as a source of 

 nitrogen. Upon the ammonium phosphate medium Ps. mcsen- 

 terica, Ps. tenuis, and XXXVI, developed. With potassium 

 nitrate, strain CXII showed a delayed growth. Xone of the 

 strains developed on the calcium nitrate medium. Ps. mcsen- 

 terica was the only strain which developed upon the medium con- 

 taining urea. 



III. Physical and Biochemical Features. 



For the purpose of determining acid production triplicate 

 titrations of cultures and controls were made after 1, 2, 4, 10, and 

 20 day incubation periods. Five cc. of the medium were pipetted 

 into 45 cc. of distilled water in Erlenmeyer flasks, boiled two 

 minutes and titrated hot with N/20 sodium hydroxid against 

 phenolphthalein. 



1. Sugar free medium. — Control titrations were made upon 

 a sugar free medium prepared as follows : 1% of Bausch & Lomb's 

 peptone was added to distilled water and steamed in a double 

 cooker about 50 minutes, tubed 10 cc. per tube, and autoclaved. 

 A small amount of acid was produced on this sugar free medium 

 by strains Ps. putrida, CXII, CXV, CXLVIII. Previous to boil- 

 ing the acid was masked by ammonia. The figures in the table 

 indicate the percent of normal acid or alkali produced. 



