"MITOGENETIC RAYS"—A CRITIQUE OF THE YEAST-DETECTOR METHOD

¹ From the Osborn Zoölogical Laboratory, Yale University, the Physiological Laboratory, Princeton University, and the Marine Biological Laboratory, Woods Hole

Yeasts (Saccharomyces cerevisi and ellipsoideus) grown in a liquid medium which was maintained effectively constant in quartz and in glass containers, were exposed to supposedly potent sources of mitogenetic radiation: bacteria (Vibrio phosphorescens and Phytomonas tumefaciens), nion roots, and the two above-mentioned species of yeast. In 58 per cent of the experiments, negative results were obtained, while in 42 per cent there was a slight positive variation which did not exceed normal control variations. No effectsof a mitogenetic radiation could be detected in the exposed yeast. In all cases the percentage range of variation of the experimental cultures was within the range of normal variation.

It is further shown that the formula used by the Gurwitsch school in calculating the induction effect is unsatisfactory because it exaggerates the variations found in the normal cultures until they appear as induction or inhibition effects.

The necessity of an effectively constant environment which does not restrict the potentially unlimited growth of the yeast is stressed. A constant environment avoids the difficulties of measurement and evaluation of the unfavorable effects of changing environments in experiments designed to test the effect of mitogenetic radiation or other stimulants of yeast growth.

Thus certain conditions and criteria are established which, it is believed, the proponents of the theory of mitogenetic radiation cannot legitimately disregard in their attempt to establish the existence of such a radiation when yeast cultures are used as detectors.

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				O. W. Richards THE ANALYSIS OF GROWTH AS ILLUSTRATED BY YEAST Cold Spring Harb Symp Quant Biol, January 1, 1934; 2(0): 157 - 166. [Abstract] [PDF]