85 



températures, which makes itself only gradually felt 

 during thc preliminary warming-tinie and was spoken of 

 in § 13, also plays a part herc V 



After the figures published by the authors I readily 

 accept their stat^ment, that this is not the case *). 



The objections stated under 1° and 2° are more im- 

 portant in my opinion, and on thèse points I am not 

 convinced by van Iterson's réfutation. It may be, that 

 diffusion acts not as a limiting factor, but surely there 

 is more than diffusion only, which constitutes a différence 

 between the reactions in question and a homogeneous 

 System, 



Van Iterson does not think the fact mentioned under 

 2° to be in support of Blackman's theory: for „what 

 is the use of Blackman's theory, if physiological pro- 

 cesses are allowed to divert from van 't Hoffs law 

 even at températures which are not harmful?" 



This last question brings me to the cardinal point of 

 this discussion. 



Blackman's theory started from the idea that van 

 't Hoffs law, which holds good for so many chemical 

 reactions, should be applicable to chemical reactions in 

 the living organism also. Van Iterson and Miss van 

 Amstel put this theory to a practical test in the cases 

 of alcoholic fermentation and inversion of cane-sugar, and 

 havc found it inapplicable. Xow they conclude that 

 Blackman's theory is to be rejected, and they say so 

 quite generally. This conclusion I did not think justified 

 by the facts and I still hold this opinion. Blackman's 



1) Of course I maiulain my opinion, that the favourable influence 

 of high températures nceds some timc to maku ils inilucncc fnlly 

 felt. The facts quotcd in » 13 arc there to pro%xit. The case ofgrowth 

 quoted l'rom Sachs is especially convinciog. 



