In juice from bottom yeast it amounts to about 5 to 10 per cent. of the total fermentation obtainable with glucose [Buchner, 1900, 2], whereas in juice from top yeasts, which gives a smaller total fermentation with glucose, it may occasionally equal, or even exceed, the glucose fermentation, and frequently amounts to 30 to 50 per cent. of it. It is therefore generally advisable in studying the effect of yeast-juice on any particular substance to ascertain the extent of autofermentation by means of a parallel experiment. The maceration extract of Lebedeff (p. 24) is usually, but not invariably [Oppenheimer, 1914, 2], free from glycogen, which is hydrolysed [p034] and fermented during the processes of drying and macerating, and therefore as a rule shows no appreciable autofermentation. (/e/) /Effect of Concentration of Sugar on the Total Amount of Fermentation./ The kinetics of fermentation by zymase will be considered later on (p. 120), but the effect on the total fermentation of different concentrations of sugar, this substance being present throughout in considerable excess, may be advantageously discussed at this stage. The subject has been investigated by Buchner [Buchner, E. and H., and Hahn, 1903, pp. 150-8; Buchner and Rapp, 1897] using cane sugar, and he has found both for yeast-juice and for dried yeast-juice dissolved in water that (/a/) the total amount of fermentation increases with the concentration of the sugar; (/b/) the initial rate of fermentation decreases with the concentration of the sugar. The following are the results of a typical experiment, 20 c.c. of yeast-juice being employed in presence of toluene at 22°:-- Cane Sugar. │ CO{2} in grams after ─────────┬───────────┼──────────┬──────────┬────────── Weight. │ Per cent. │ 6 hours. │24 hours. │ 96 hours. ─────────┼───────────┼──────────┼──────────┼────────── 2·2 │ 10 │ 0·17 │ 0·50 │ 0·55 3·52 │ 15 │ 0·14 │ 0·53 │ 0·64 5 │ 20 │ 0·13 │ 0·54 │ 0·73 6·66 │ 25 │ 0·13 │ 0·52 │ 0·80 8·56 │ 30 │ 0·12 │ 0·46 │ 0·81 10·76 │ 35 │ 0·12 │ 0·40 │ 0·82 13·33 │ 40 │ 0·11 │ 0·36 │ 0·82 10·76 │ 35 │ 0·12 │ 0·40 │ 0·82 13·33 │ 40 │ 0·11 │ 0·36 │ 0·82