Page:Popular Science Monthly Volume 50.djvu/617

Rh incredible power of growth and reproduction. This growth is wholly controlled by external conditions and by the composition of the nutrient medium. Probably no form of life approaches in power of rapid reproduction these minutest plants, the bacteria and yeasts, and none are probably more delicately responsive to varying conditions of life.

Yeast is able to grow until, by decomposition of sugar, its medium comes to contain fourteen per cent of common alcohol. At this point, no matter how much sugar and other nutriment remains, further growth is impossible.

Now, of especial interest to the physiology of nutrition, and the influence upon it of waste products generally, is the question,



What effect have very minute quantities of alcohol on the growth of yeast?

Fig. 1 represents to the eye, in the diagram to the left, the four possible kinds of action in the four lines diverging from the point marked "per cent." If no slowing effect is present until the poison limit, fourteen per cent, is reached, the line marked "normal" should be continued out until directly over a point corresponding to fourteen per cent strength of solution, and then should drop perpendicularly to the zero point of growth on the base line. As a matter of fact, Flügge states that growth is slowed with twelve per cent and stopped at fourteen per cent. If this be true, instead of dropping vertically, it would fall a little obliquely from twelve per cent to fourteen per cent. This