1068 BIOLOGICAL EFFECTS OF RADIATION 



for most reactions which involve organic compounds. This means that 

 the reaction velocity or rate of respiration is at least doubled for each 

 10° rise in temperature, but at all temperatures above 20°C. the Qio ratio 

 tends to become progressively smaller as the temperature rises. The 

 exact influence of heat, therefore, depends in part on the specific heats of 

 all substance involved but such differences are merely quantitative. 



RADIATION AND FERMENTATION 



The only phase or type of fermentation which has been studied for its 

 relations with the various forms of radiant energy is alcoholic fermenta- 

 tion. Although this process is associated with other genera of plants, 

 the few observations reported have all been made for yeast. The three 

 forms of radiation which have been tested thus far are visible light, ultra- 

 violet and X-rays. In addition, the heat effect will be discussed only 

 briefly because it is not essentially different for this special phase of 

 katabolism. 



Light. — Although others have observed the relation of cell division in 

 yeast to its illumination, with a general agreement that a bright light 

 source retards the production of new cells, there have been only two 

 reports of the effect on fermentation itself. The first was a dissertation 

 by Lohmann in 1896. The second was made by Lubimenko and Froloff- 

 Bagreief (10) in 1912. Since the latter is more available and definitely 

 confined to the question of fermentation as opposed to cell division, it 

 will be used as a basis of discussion. These workers agreed with the 

 findings of Lohmann and included additional precautions to observe the 

 direct effect of the radiation on the process of fermentation. 



The conclusion is that light retards fermentation. This is the natural 

 result, since it also reduces the number of cells available to produce CO2 

 and alcohol and a part of the effect is due to this relationship. However, 

 Lubimenko and Froloff-Bagreief claim, from results not published in 

 detail, that some of the effect is an actual lowering of the rate of fermenta- 

 tion. They also report less glycerin and more acid in their tests with 

 raisin must. The depression in the fermentation rate is said to be more 

 pronounced as the temperature is increased. 



Since this conclusion is not in accord with the effect of light on respira- 

 tion and because the only data available have been incompletely reported, 

 the result is far from conclusive. The experiments must be repeated for 

 yea.st and likewise performed with other causal agents of fermentation. 

 Ultra-violet Rays. — For the effect of these short waves on fermenta- 

 tion we have the recent work of Lindner (8) who undertook to repeat the 

 pioneer test made by Fazi in 1915. Because of the improved technique 

 of Lindner, his results are the first real proof of a remarkable acceleration 

 of fermentation by the radiation from a mercury-vapor lamp. The 

 temperature was not held constant but the change in rate of CO2 pro- 



