4 BIOLOGICAL TIME 



separate the chemical phenomena from their evolution^ from 

 their correlation in time, for these are two entirely different 

 things.'^ As synthetic actions, it is evident that these 

 phenomena reveal only general chemical forces. By 

 examining them successively one by one this is clearly 

 demonstrated. The calcareous matter which is found in 

 the shells of molluscs, in birds' eggs, in the bones of 

 mammals, is certainly formed according to the laws of 

 ordinary chemistry during embryonic evolution. Fatty and 

 oily substances are in the same case, and chemistry has 

 already succeeded in reproducing artificially, in the labora- 

 tory, a great number of immediate principles, of essential 

 oils and of complex bodies which are the apanage of the 

 animal and of the vegetable kingdoms. Starchy substances 

 which are developed in animals and which reproduce them- 

 selves in the green leaves of plants by the combination of 

 carbon and water under the influence of the sun, are also 

 well-characterized chemical phenomena. If the synthetic 

 properties of nitrogenous substances are much less clear, 

 this is due to the fact that organic chemistry is not far 

 enough advanced as yet. But it is nevertheless certain 

 that the substances are built up in living beings by chemical 

 methods. In truth, it may be said that the germs and the 

 cells, elements of organic synthesis, are most exceptional 

 agents. In respect to the phenomena of disorganization it 

 might also be said that enzymes are special factors charac- 

 terizing living matter.^ The following seems to be a 

 general law. Chemical phenomena in the organism are 

 produced by special agents or processes. But this does 

 not alter the purely chemical nature of the phenomena 

 which take place, nor of the products which are their 

 result. 



'And now we come to organic evolution. The agents of 



^ The italics are mine. — L. D. N. 



^ Due to the remarkable work of Gabriel Bertrand, the funda- 

 mental role of infinitesimal traces of metals in the activity of the 

 enzymes is now known, but so far it has been possible to synthesize 

 artificially only one of them. (Kuhn, 1934.) 



