Influence of the Concentration of Yeast.
It appears to be well established that, when changes in the quantity and constitution of the yeast employed are eliminated, the rate of fermentation is exactly proportional to the number of the yeast-cells present (Aberson, Slator). This result might be anticipated, as pointed out by Slator, from the fact that the fermentation takes place within the cell, each cell acting as an independent individual.
The diffusion of sugar into the yeast-cell which necessarily precedes the act of fermentation has been shown by Slator and Sand [[1910]] to occur at such a rate that the supply of sugar is always in excess of the amount which can be fermented by the cell.