Methylglyoxal, CH{3}·CO·CHO, has been tested by Mayer [1907] and Wohl [1907, 2] with yeast, and by Buchner and Meisenheimer both with acetone-yeast [1906] and yeast-juice [1910], in every case with negative results, but it may be noted that the concentration employed in the last mentioned of these experiments was such as considerably to diminish the autofermentation of the juice. Glyceraldehyde, CH{2}(OH)·CH(OH)·CHO, was also tested with yeast with negative results by Wohl [1898] and by Emmerling [1899], who employed a number of different yeasts. The same negative result attended the experiments of Piloty [1897] and Emmerling [1899] with pure dihydroxyacetone. Fischer and Tafel [1888, 1889], however, had previously found that glycerose, a mixture of glyceraldehyde and dihydroxyacetone prepared by the oxidation of glycerol, was readily fermented by yeast, agreeing in this respect with the still older observations of Van Deen and of Grimaux. The reason for this diversity of result has not been definitely ascertained, but it has been supposed by Emmerling to lie in the formation of some fermentable sugar from [p105] glycerose when the latter is subjected to too high a temperature during its preparation. On the other hand, Bertrand [1904] succeeded in fermenting pure dihydroxyacetone by treating a solution of 1 gram in 30 c.c. of liquid with a small quantity of yeast for ten days at 30°, the best result being a fermentation of 25 per cent. of the substance taken. Moreover, Boysen-Jensen [1908, 1910, 1914] states that he has also observed both the formation from glucose and the fermentation of this substance by living yeast, but the amounts of alcohol and carbon dioxide produced were so minute and the evidence for the production of dihydroxyacetone so inconclusive that the experiments cannot be regarded as in any way decisive [see Chick, 1912; Euler and Fodor, 1911; Karauschanoff, 1911; Buchner and Meisenheimer, 1912]. A careful investigation by Buchner [1910] and Buchner and Meisenheimer [1910] has led them to the conclusion that both glyceraldehyde and dihydroxyacetone are fermentable. Glyceraldehyde exerts a powerful inhibiting action both on yeast and yeast-juice, and was only found to give rise to a very limited amount of carbon dioxide, quantities of 0·15 to 0·025 gram being treated with 1 gram of yeast or 5 c.c. of yeast-juice and a production of 4 to 12 c.c. of carbon dioxide being attained.