224 
Brown. — Some Studies on Yeast . 
That this was a wrong interpretation of the facts was conclusively 
shown by Adrian Brown (Journ. Chem. Soc., Trans., 1892, p. 61 ; ibid., 1894, 
1911), who has brought forward unmistakable evidence,' proving that yeast 
well supplied with free oxygen possesses as much or even more fermentative 
power than the same yeast under conditions of oxygen starvation ; and 
more recently this has been confirmed by A. Slator. But the errors of 
great men live long after them, and it will no doubt require another 
generation of workers to eliminate the statement from the text-books. 1 
Whatever truth there may be in the view that the breaking down of 
the sugar molecule, and the resulting liberation of energy, is due to the 
cell protoplasm abstracting and appropriating some small constituent part 
of the sugar molecule, this hypothesis receives no support from the conjoint 
study of the reproductive and fermentative functions of the cell, which are 
certainly not inversely related to each other. 
It will help us if we consider for a moment the behaviour of a yeast- 
cell bathed in a suitable nutrient liquid, at a time when the free oxygen 
originally dissolved in the liquid has been completely absorbed by the 
yeast, and when the c oxygen charge’ of the cells has completely spent 
itself in several successive generations of subdivision. As we have seen in 
Part I of this paper, no further reproduction is possible under these con- 
ditions, if access of oxygen from without is prevented, but the cells speedily 
acquire a static condition of equilibrium with regard to the medium, and 
this condition remains constant for some time. During this period it can 
be experimentally demonstrated that the average mass and composition of 
the cells remain constant ; in other words, regarded from the point of view 
merely of cell-maintenance, the normal katabolic and anabolic processes, if 
they still exist at all, must just balance each other, and little or no further 
extraneous supply of energy is required to continue the life of a cell so 
placed. Notwithstanding this, we find under these apparently static con- 
ditions of maintenance an enormous activity in the metabolic 4 mill ’, through 
which continues to pass an amount of substance which, under certain con- 
ditions of temperature, may amount to several times the mass of the cell in 
a few hours, and a corresponding liberation of energy sufficient to raise the 
cell-temperature to a very high point. 
It may be argued that this apparent waste of energy is due to the 
necessity of the yeast-cell having to share its temperature with the surrounding 
medium, which is one of high specific heat, but under any circumstances it 
is difficult to see how any rise of temperature in the medium can be of any 
use to the cell under the above conditions, since such a rise can only 
stimulate the ‘mill’ to a further output of work which appears to be 
1 Quite recently I have heard of a proposed improvement in wine-making which was entirely 
based on this fundamental error of assuming the inverse relation of the reproductive and fermentative 
faculties of yeast. 
