274 Transactions of the Canadian Institute. [vol. ix 



ferment, as it was called. And this kind of fermentation was kept always 

 strictly distinct from fermentations brought about by unorganized 

 ferments, or enzymes as they were called by Kiihne, chemical substances, 

 that is, that are active as ferments where there is no life. Two totally 

 distinct causes of fermentation were recognized: life and enzymes. 

 When therefore what had always been regarded as the crucial instance 

 of the fermentative action of life was found to be nothing of the kind, 

 there was a movement about the foundations of physiological belief. 



Enzymes were before this known as substances excreted by certain 

 cells that brought about certain changes in other substances in the en- 

 vironment of the cells, changes which were in some way necessary for 

 facilitating the assimilation of food. The digestive enzymes of the gas- 

 tric or pancreatic juice or of the saliva might serve an important function 

 contributing to the life of an organism, but it was an ancillary function, 

 little more than a culinary operation. But here was an enzyme normally 

 operating within the organism, the cause of the most striking mani- 

 festation of its life, suddenly proved to be removable from the organism, 

 though it is true only by special measures, and capable of operating after 

 all other signs of life had ceased. 



The surrender of this point need not involve, and has not involved, 

 the surrender of the whole position. Alcoholic fermentation is only one 

 among myriads of changes that we have been in the habit of attributing 

 to vital activity. But it has made obvious, what was often overlooked 

 before, that in regarding life as the cause of the chemical reactions under- 

 lying the phenomena of life we are indulging ourselves in a verbal illusion. 



There is a convenient term in common use among physiologists — 

 first introduced into the language by Sir Michael Foster thirty years 

 ago or more — metabolism, a general name under which he intended to 

 include all the chemical transformations which go to make the life of an 

 organism. These changes may be constructive or anabolic, or they may 

 be destructive or catabolic; growth, assimilation, repair are effected by 

 anabolic change: the evolution of energy as heat or work, decay and 

 death by cataboliC. At all moments of the life of an organism both 

 phases of its chemical life are in operation side by side, and every 

 manifestation of its life is accompanied by, or an expression of some 

 chemical change. Food is taken in, digested, assimilated and so altered 

 as to become part of the living body and of the material in which its 

 life is exhibited . Every activity of the body involves some chemical change 

 in the living substance, and a certain proportion of this substance is at 

 each moment so far changed as to be incapable of further participation 

 in its life, and is then expelled and returned to the condition of inanimate 

 matter. Each step is a chemical reaction or a complex system of 



