Yeast-juice brings about a slow fermentation of those sugars which are fermented by the yeast from which it is prepared as well as of dextrin, and of starch and glycogen, which are not fermented by living yeast. (/a/) /Relation to Fermentation by living Yeast./ Both in rate of fermentation and in the total fermentation produced, yeast-juice stands far behind the equivalent amount of living yeast. Taking 25 c.c. of yeast-juice to be equivalent to at least 36 grams of pressed yeast containing 70 per cent. of moisture, it is found that whereas the yeast-juice (from English top yeast) gives with glucose a maximum rate of fermentation of about 3 c.c. in five minutes, the living yeast ferments the sugar at the rate of about 126 c.c. in the same time, or [p030] about forty times as quickly. The total carbon dioxide obtainable from the yeast-juice, moreover, corresponds to the fermentation of only 2 to 3 grams of sugar, whilst the living yeast will readily ferment a much larger quantity, although the exact limit in this respect has not been accurately determined. The reasons for this great difference in behaviour will be discussed later on, after the various factors concerned in fermentation have been considered (p. 123). (/b/) /Relation of Alcohol to Carbon Dioxide./ In all cases of fermentation by yeast-juice and zymin, the relative amounts of carbon dioxide and alcohol produced are substantially in the ratio of the molecular weights of the compounds, that is as 44: 46, so that for 1 part of carbon dioxide 1·04 of alcohol are formed. This has been shown for the juice and zymin from bottom yeasts by Buchner [Buchner, E. and H., and Hahn, 1903, pp. 210, 211], who obtained the ratios 1·01, 0·98, 1·01, and 0·99 from experiments in which from 8 to 15 grams of alcohol were produced. Similar numbers, 0·90, 1·12, 0·95, 0·91 and 0·92, have been obtained for the juice from top yeasts by Harden and Young [1904], who worked with much smaller quantities. The variable results obtained with juice from top yeast by Macfadyen, Morris and Rowland [1900], have not been confirmed. (/c/) /Relation of Carbon Dioxide and Alcohol Produced to the Amount of Sugar Fermented./