(598 ) 
Physiology. — “The temperature-cplinum of physiological pro- 
cesses.’ By Miss. J. van AmsreL and Prof. G. VAN ÍTERSON Jr. 
(Communicated by Prof. M. W. BeIJERINCK). 
(Communicated in the meeting of October 29, 1910). 
Since the appearance of our first paper on the temperature opti- 
mum of physiological processes, *) a communication was published by 
Mr. A. A. L. Roroers ®) “Influence of temperature on the geotropic 
praesentation time of Avena sativa”. 
Beside the discussion of the highly interesting and accurate obser- 
vations concerning the said subject, this paper gives a comparison 
of the results obtained by Mr. Rereers with those of other experi- 
menters, and our paper, referred to above, is more specially sub- 
mitted to criticism in it. Considering that the detailed record of the 
values on which our preliminary publication is based may still stay 
out some time, we thought it desirable already now to vindicate 
the conclusions which we have drawn from our results against the 
objections advanced by Mr. Rurcers. At the same time we use this 
opportunity to indicate some new considerations in support of our 
views. 
It may be called to mind that we had studied the relation be- 
tween temperature and fermentation velocity, such as it appears after 
mixing a yeast suspension with an excess of glucose solution and 
after the so-called “Antrieb” is past*). Thereby it was found that 
in contradiction with what after the theory of DucLaux-BLACKMAN 
might have been expected, already before a lasting noxious influence 
of the temperature on the fermentation function becomes perceptible 
a distinct deviation from the rule of Van ’r Horr sets in, which is 
even so great that the velocity-temperature-curve changes in respect 
to the temperature axe from convex to concave. 
For different fore-heating periods (5, 10, 15 and 20 minutes) one and 
the same curve for the relation between velocity and temperature was 
found, as might be expected a priori. At noxious temperatures this 
relation for the 4 mentioned times of fore-heating is also represented 
by + different curves, and by now stating at a determined time of 
foreheating and a determined temperature what part of the yeast 
1) These Proceedings June 25, 1910 p. 227. 
2) These proceedings Oct. 29, 1910 p. 476. In Mr. Rureers’ Dissertation the 
same subject is treated elaborately. 
3) For the sake of simplicity we leave out for the moment the inversion of 
cane sugar, which was studied by us in a corresponding way. 
