456 HEPBURN AND ST. JOHN— BIOCHEMICAL STUDIES 



day. On the tenth day, the medium was still alkaline in three experi- 

 ments, and had become distinctly acid in two experiments, while the 

 change from an alkaline to an acid reaction was almost, but not entirely, 

 complete in the sixth experiment. 



In the seventh experiment, colonies were absent on the third day, 

 but had developed by the tenth day, and had caused the entire medium 

 to assume an alkaline reaction. 



Ammonium lactate rosolic acid agar. Six experiments were char- 

 acterized, on the third day, by good growth of the bacteria and an 

 alkaline reaction of the medium. On the tenth day, the reaction of the 

 medium had begun to change from alkaline to acid in five of these ex- 

 periments. 



In the seventh experiment, growth of the bacteria had not occurred 

 by the third day, but had taken place by the tenth day, and the medium 

 had then become alkaline in reaction. 



In the set of seven experiments, which were studied on all four 

 rosolic acid agars — asparagin, glycocoU, acetamide, and ammonium 

 lactate — the odor was also recorded. The plates were quite frequently 

 characterized on the third day by an odor recalling that of ammonia or 

 amines. This odor was rarely noted on the tenth day. 



Protein liquid medium. The bacteria of the pitcher liquor were per- 

 mitted to act on the suspension of protein (from aleuronat) in the stock 

 solution of inorganic salts. Two series, of 8 experiments each, were 

 made. In each experiment, 1 cc. of pitcher liquor was added to a tube 

 of the medium. 



In the first series of experiments, the test for indol was made after 

 incubation for three days, and again after incubation for ten days. 

 The test was always negative. 



In the second series of experiments, neither indol nor free tryptophane 

 was present after incubation for twelve days. 



Lactose bile-salt bouillon. In two experiments, 1 cc. of pitcher liquor 

 was sown in lactose bile-salt bouillon; gas developed within 72 hours, 

 showing the presence of organisms of the colon-aerogenes group in both 

 pitchers. 



The liquor from several pitchers was mixed, and five tubes of the 

 bouillon were inoculated, using 1 cc. of the mixture, and of its 1:10, 

 1:100, 1:1,000, and 1:10,000 dilutions, respectively. Gas developed in 

 all five tubes within 72 hours, hence it may be stated that at least 10,000 



