114 ORGANISM AND MECHANISM 



of which the absorption of oxygen is taken as an index, is 

 regular and constant, and cannot be expressed either by 

 Arrhenius's formula or by the rule of Van't Hoff. Ege 

 and Krogh have shown that Van't HofTs rule does not apply 

 to the relation between temperature and the respiratory 

 exchange in goldfishes. Indeed, there are many cases where 

 Van't Hoff's rule does not seem to apply. It is said to held 

 good for such a subtle thing as the rate of cell-division in 

 the growing point of a root, but this is not to be taken as 

 indicating a simple chemical process. There appears to be 

 a repertory of intricate processes, the peculiarities of which 

 are mutually neutralised. 



There are also some difficulties in regard to the trans- 

 formations of energy in living creatures that make one hesi- 

 tate to assert dogmatically that conclusions based on a study 

 of the inorganic must hold true for organisms. It is pos- 

 sible, for instance, that living cells may act selectively in 

 relation to the molecules that bombard them, and that the 

 organism may be able in some measure to evade the sec- 

 ond law of thermodynamics. 



The best steam-engine is only able to change about 12 

 per cent, of its income of potential energy into work; the 

 animal can change about 25 per cent, and is therefore from 

 this point of view quite remarkably efficient. Moreover, 

 as Professor Soddy points out, the organism has a capacity 

 for dealing with kinds of chemical substances which cannot be 

 converted by inanimate agencies into useful forms of energy 

 without terrible waste. " The chemical energy of food suf- 

 fers direct transformation into work without first being 

 converted into heat." 



In any case it is well to remember that while there is a 

 general, and for certain purposes very useful, applicability 



