71 



bo,uillon. The closed end and inner one-fourth of the U were still 

 perfectl}^ clear. On the twelfth day the line of demarcation in the U 

 was less distinct and there was a faint haze in the lower part of the 

 closed end (3 cm.). On the twenty-third day the faint haze had involved 

 the whole of the closed end, but had not become any denser, i. e., the 

 clouding- in the closed end was not one one-hundredth part that in the 

 open end. The fluid was feebly alkaline at the beginning of the exper- 

 iment and was decidedly acid (to neutral litnuis paper) at the close, i. e., 

 the reaction was in marked contrast to that of the glycerin bouillon. 

 Both tubes of the maltose bouillon behaved alike. They had been pro- 

 tected from jarring and inequalities of temperature, and steaming for 

 50 minutes at the close of the experiment did not clause the formation 

 of any air bubble in the closed end. This very feeble clouding in the 

 closed end after the second week would seem therefore to be due either 

 to some contaminating substance in the maltose or else to that sub- 

 stance itself. 



(4) The nitrate bouillon (stock 474) was also tested in fermentation 

 tub^s. Two tubes were inoculated from solid cultures 7 days old. Both 

 clouded on the second day, both remained entirely clear in the closed 

 end and inner one-fourth of the U until after the eighth day. On the 

 fourteenth day both were feebly clouded in the whole of the closed 

 end. No gas was formed and the fluid remained strongl}^ alkaline. 



On steaming these two tubes a bubble appeared in the closed end of 

 each, and the feeble clouding was consequently attributed to growth 

 stimulated by the presence of air absorbed from the open end. 



The closed end of fermentation tubes fllled with the following sub- 

 stances and inoculated with Ps. campestrk remained entirel}'- free from 

 clouding: Potato broth; cabbage broth; cauliflower broth; peptone 

 water with grape sugar, fruit sugar, cane sugar, milk sugar, galactose, 

 maltose, dextrin, and glycerin. The open end clouded. 



Dibasic calcium phosphate added in 5, 10, 20, and 30 milligram 

 doses to test tubes holding 10, 15, and 20 c. c. of a peptone water con- 

 taining grape sugar and glycerin, doubled the growth of Ps. cainpestris. 

 Other species were not tried. This fluid was then tested in fermen- 

 tation tubes. The calcium salt stiumlated growth in the open end, but 

 the closed end remained clear for three weeks. Afterwards there was 

 clouding. This stock consisted of 200 c. c. of Altered Potomac water, 

 2 grams of Merck's c. p. anhydrous grape sugar, 4 c. c. of Schering's 

 glycerin, and 2 grams of Witte's peptonum siccum; the whole dried 

 out one-half by long standing and diluted with three times its hulk of 

 di.stilled water before flUing into the tubes and adding the phosphate. 



Dibasic sodium phosphate used in the same stock also favored the 

 growth of Ps. cainpestris. 



From the above account it will be seen that in various ways the 

 behavior of Ps. hyaclntld in fermentiition tubes closely resembles that 



