The Evolution of the Sciences 



matter of these strange products, enzymes or 

 zymases, which are frequently designated under 

 the generic name of soluble ferments, to indicate 

 that they transform the substance of living 

 beings, as a pinch of leaven modifies a batch 

 of dough. 



Enzymes are the soul of the many vital 

 reactions, the demon ceaselessly busy tying 

 and untying the molecular bonds. Already 

 considerable numbers have been discovered 

 and isolated, which all present a common 

 character. Their mass is always very small 

 in comparison with the mass of the body trans- 

 formed; rennet, for example, can curdle ten 

 thousand times its weight of milk. Thus the 

 enzymes act like ferments but without being 

 organised; and, as a matter of fact, organised 

 ferments act only through the enzymes secreted 

 by them, as Buchner established in 1897 in the 

 case of the enzyme of yeast. 



The action of enzymes is beginning to be 

 understood. M. Bertrand has succeeded in 

 the case of some of them, the oxidases, in de- 

 termining the function of the manganese of 



which they contain an infinitesimal proportion. 



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