It has further been found that arsenates, and to a less degree arsenites, also produce an acceleration of the rate of autofermentation of yeast-juice and of the rate at which glycogen is fermented. This turns out to be due in all probability to an increase in the activity of the glycogenase by the action of which the sugar is supplied which is the direct subject of fermentation. Thus in one case an initial rate of fermentation of glycogen of 1·9 c.c. per five minutes was increased by 0·05 molar arsenate to 9·7 and the amount of carbon dioxide evolved in two hours from 38 to 158 c.c. Even this enhanced production of glucose from glycogen, however, is not nearly sufficient for the complete utilisation of the phosphate also being liberated by the action on the hexosephosphatase, for the addition of an excess of sugar produces a much higher rate, in this case 36 c.c. per five minutes. The effect of arsenate on the rate of action of the glycogenase seems therefore to be much smaller than on that of the hexosephosphatase. No other substances have yet been found which share these interesting properties with arsenates and arsenites, and no advance has been made towards an understanding of the mechanism of the accelerating action of these salts on the specific enzymes which are affected by them. [p081] CHAPTER VI. CARBOXYLASE. An observation of remarkable interest, which promises to throw light on several important features of the biochemistry of yeast, was made in 1911, and has since then formed the subject of detailed investigation by Neuberg and a number of co-workers. It was found that yeast had the power of rapidly decomposing a large number of hydroxy-and keto-acids [Neuberg and Hildesheimer, 1911; Neuberg and Tir, 1911; see also Karczag, 1912, 1, 2]. The most important among these are pyruvic acid, CH{3}·CO·COOH, and a considerable number of other aliphatic a-keto-acids which are decomposed with evolution of carbon dioxide and formation of the corresponding aldehyde:-- R·CO·COOH = R·CHO + CO{2}.