896 TRANSACTIONS OF SECTION K. 



been generalised into a rule by van't Hoff. As this increase is repeated for each 

 successive rise of 10'' C. either by the same factor or a somewhat smaller one, the 

 acceleration of reaction-velocity by temperature is logarithmic in nature, and the 

 curverepresenting itrisesever moreandmoresteeply. Thus keeping within the vital 

 range of temperature a reaction with a temperature factor of x 2 per 10° C. will 

 go sixteen times as fiist at 40° C. as at 0° C, while one with a factor of x 3 

 will go eighty-one times as fast. 



This general law of the acceleration of reactions by temj)erature holds equally 

 for reactions which are being accelerated by the presence of catalysts. As we 

 f^gard the catalyst as merely providing for the particular reaction it catalyses, a 

 quick way round to the final stage by passing through the intermediate stage of 

 forming a temporary addition-compound with the catalyst itself, so we should 

 expect rise of temperature to accelerate similarly these substituted chemical 

 reactions. 



If this acceleration is a fundamental principle of chemical mechanics it ia 

 quite impossible to see how vital chemistry can fail to exhibit it also. 



ACCELEKAXION OF VlTAL PROCESSES BT TeMPERATTIEE. 



At present we have but a small number of available data among plants to 

 Consider critically from this point of view. But all the serious data with which 

 I am acquainted, which deal with vital processes that are to be considered as part 

 of the protoplasmic catalytic congeries, do exhibit this acceleration of reaction- 

 velocity by temperature as a primary eifect.' 



Let U8 briefly consider these data. On the katabolic side of metabolism we 

 have the respiratory production of CO^, and opposed to it on the anabolic side the 

 intake of carbon in assimilation. 



As a measure of the rate of the metabolic processes constituting growth we 

 have data upon the division of flagellates : and finally there is the obscure process 

 of circulation of protoplasm. 



The intensity of CUj production is often held to be a measure of the general 

 intensity of metabolism, but any relation between growth-rate and respiration 

 has yet to be clearly established. Our science is not yet in the stage when 

 quantitative work in relation to conditions is at all abundant ; we are but just 

 emerging from the stage that chemistry was in before the dawn of physical 

 chemistry. 



Taken by itself the CO^-production of an ordinary green plant shows a very 

 close relation with temperature. In the case of the cherry-laurel worked out 

 by Miss Matthsei and myself the respiration of cut leaves rises by a factor of 

 2'1 for every 10° C. (See fig. 5, llesp.) This has been investigated over the 

 range of temperatures from 16° C. to 45° C. At this higher temperature the 

 leaves can only survive ten hours in the dark, and their respiration is aflected in 

 quite a short time, but in the initial phases the CO^ output has the value of 

 0:^10 gr. per hour and unit weight of leaf, while at ltj°*2 (J. the amount is only 

 0-0025 gr. CO.j. Thus the respiration increases over a range of tenfold with perfect 

 regularity solely by increase of temperature. No reaction in a test-tube could 

 show less autonomy. At temperatures above 45° C. the temperature still soontr 

 proves fatal unless the leaf is illuminated so as to carry out a certain amount 

 of photosynthesis and compensate for the loss of carbon in respiration. Thus, 

 with rising temperature, tliere is at no time any sign of an optimum or of a 

 decrease of the intensity of the initial stage of respiration. 



Here, then, on the laiabolic side of metabolism we have no grounds for 

 assuming that 'temperature-stimuli' are at work regulating the intensity of pro- 

 toplasmic respiration, but we find what 1 can only regard as a purely physical- 

 chemical effect. The numbers obtained by Clausen- for the respiration of seedlings 

 and buds at different temperatures indicate a temperature coefficient of about 

 2-5 for a rise of 10° C. 



' A collection of twenty cases, mostly from animal physiology, by Kanitz {leits, 

 fur ElcMroclu'viie, 1907, p. 707), exhibits coefficients ranging from 1*7 to G'3. 

 2 LandwirtsfhiiftUche Jahrbiichcr, Bd. X'X, IS'JO, 



