25 



der of the 10 c. c. of gelatin ayrs unchangod, the stab fadincr out in the 

 depths to scattered round white colonies. 



It would seem, therefore, that excess of malic aid favored liquefac- 

 tion and the production of the yellow pigment. Possil)ly, however, 

 these results are to ])e ascribed soleh' to changes in the ph^^sical char- 

 acter of the gelatin. The melting point was slighth' reduced by the 

 addition of the acid and was lowest in the stocks which received 

 the most acid. 



The most growth obtained on any gelatin was with +51 malic acid 

 gelatin to which 10 per cent of cane sugar had been added. This was 

 a slant culture kept in the ice chest at lU" to 25^ C, for 0^ months, 

 during all of which time it was overlooked, so that if there was anj- 

 retardation of growth at lirst, there is no record of it. When exam- 

 ined at the end of 6^ months, there was a most copious growth, but no 

 trace of liquefaction. At some time during the summer the ice was 

 allowed to get low and the gelatin melted, allowing a copious bright 

 3'ellow surface growth to fall to the bottom. Subsequent! 3', with the 

 addition of more ice, the gelatin resolidified and a new surface growth 

 formed. AVhen examined at the end of the 0^ months, there was a 

 dense l)right yellow rim 12 to 15 mm. wide, and a copious surface 

 growth separated from the 3^ellow precipitate, alread3^ mentioned, by 

 a mass of solid gelatin free from browning and clear, except for tin3" 

 scattered masses of bacteria imprisoned when the gelatin resolidified. 

 The bright 3'elloAv surface slime was still alive. 



In the -1-1:8 gelatin with 5 per cent cane sugar, at the end of 10 da3^s, 

 at 8° to 20^ C. (mosth' under 15^ C), there was a compact bright 3^el- 

 low surface growth, 12 mm. in breadth and a distinct stab, but no 

 liquefaction. This experiment was repeated at 12^ to 20"^ C, using 

 both -1-18 and -|-51 gelatin with 5 per cent cane sugar and contijuiing 

 the experiment 30 days. During this time there was no liquefaction 

 whatever in the +51 gelatin and only a ver3' feeble liquefaction in the 

 +18 gelatin, i. e., the distincth^ 3'ellow surface growth, 5 or 6 mm. in 

 diameter, was sunken in slightly. In another experiment with +18 

 and +51 gelatin with 10 per cent cane sugar, kept at 7° to 21^ C. 

 (most of the time above 11'^ and below 19-), there Avas no liquefaction 

 in 19 days. 



The same results were obtained with gelatin (stock 211c), to which 

 10 per cent cane sugar Avas added. After (U davs at 15^ to 20^ C. 

 there Avas no liquefaction whatever in one tube and onh^ the ver3^ 

 slightest in the other, and no brown stain in either. The groAvth Avas 

 better than in tul)es of sugar-free gelatin Avhich liquefied. 



There can be no doubt, therefore, that, Avhile poAverfulh^ stimulating 

 growth, cane sugar in small doses retards and in large doses entireh^ 

 inhibits the licjuefaction of the gelatin, Avhether the medium is acid or 

 alkaline. 



