Page:Popular Science Monthly Volume 50.djvu/618

598 would mean that up to a very high limit of concentration alcohol is absolutely harmless, that at a certain point it becomes suddenly toxic, and that slight increase beyond this concentration worked very rapidly to bring growth to a standstill.

A second possibility would be represented by a straight line, "Z," dotted line, falling uniformly from zero per cent to fourteen



per cent. This would indicate that the effect of the presence of alcohol in the culture medium upon yeast growth was a purely mechanical effect, a matter of friction, a clogging of the molecules, as it were. This would signify, the less alcohol the better, but that a small quantity has a comparatively slight effect, and that probably no harm is done in the way of changing the chemical reactions concerned in the growth processes of the yeast plant.

A third possibility, represented by dotted line "Y" in the figure, is in line with an idea not infrequently carried into practice, viz., that a little alcohol increases, "stimulates," activity, a larger quantity interferes with it. If this were found to be the case, the important matter to determine would be at what point of concentration alcohol ceases to be beneficial.

The heavy line, "M," represents the fourth possibility, viz., that minute amounts of alcohol have relatively a much greater retarding effect upon the growth of yeast than larger amounts. The line is plotted from the results of a series of experiments, of which a different expression is given in the diagram to the right in the figure. One thousandth of one per cent is seen to cause