4 o THE MECHANISM OF LIFE 



platinum black are all instances of catalysis. Fermentation 

 by means of a soluble ferment or diastase, a phenomenon 

 which may almost be called vital, is also a catalytic action. 

 The action of pepsin, of the pancreatic ferment, of zymase, and 

 of other similar ferments has a great analogy with the purely 

 physical phenomenon of catalysis. The diastases are all 

 colloids, and so are many other catalyzers. 



A catalyzer is a stimulus which excites a transformation of 

 energy. The catalyzer plays the same role in a chemical 

 transformation as does the minimal exciting force which sets 

 free the accumulation of potential energy previous to its 

 transformation into kinetic energy. A catalyzer is the friction 

 of the match which sets free the chemical energy of the 

 powder magazine. 



Bredig has studied the catalytic decomposition of hydrogen 

 peroxide by metallic colloids prepared by his electric method. 

 He found that 1 atom-gramme of colloidal platinum gives 

 a sensible catalytic effect when diluted with TO million 

 litres of water. Caustic soda and other chemical substances 

 inhibit the catalytic action of colloidal platinum in the same 

 way as they inhibit the fermenting action of diastase. The 

 curve of decomposition of hydrogen peroxide by colloidal 

 platinum may be compared with the curve of fermentation by 

 emulsin. Both are equally affected by the addition of an 

 alkali. Many other chemical and physical agents have a 

 similar inhibitory action on the catalysis of colloidal metals 

 and on diastasic fermentation. Thus a mere trace of sul- 

 phuretted hydrogen or hydrocyanic acid will paralyse the 

 action of a colloidal metal, just as it does that of a ferment. 

 This is what Bredig calls the poisoning of metallic ferments. 



We may hope that the further study of catalysis, a purely 

 physico-chemical phenomenon, may throw more light on the 

 mechanism of diastasic fermentation, which is essentially a vital 

 reaction. 



It must not be forgotten that all classification is artificial 

 and arbitrary, and only to be used as long as it facilitates 

 study. This observation is particularly applicable to the 

 classification of substances into crystalloids and colloids. 



