POISONS AND CATALYSTS 163 



there is a "vital chemistry" different from ordinary 

 chemistry. Some of the most peculiarly vital 

 chemical processes have lately been found to be 

 precisely similar to those that occur in mineral 

 and inorganic chemistry. Thus fermentation, once 

 thought to depend upon living organisms, is now 

 known to do so only indirectly. Directly, fermenta- 

 tion processes are due to unorganised "enzymes," 

 secreted by the organism, and these enzymes are 

 analogous to the "catalysts" of inorganic chemistry. 

 A suggestive point is that such catalysts finely 

 divided platinum metal is one of the commonest 

 used are "poisoned" by the same poisons arsenic, 

 prussic acid, and so on as are most deadly to life. 

 This means that the chemical processes occurring in 

 the living body, through the presence of enzymes, 

 are largely of the same character as those that occur 

 with mineral substances in presence of finely divided 

 platinum and similar "catalysts." The poison acts 

 by destroying the peculiar activities of these catalysts, 

 and so stops the processes they bring about. 



I do not wish to imply that bio-chemistry, as yet, 

 has been reduced to a special branch of ordinary 

 chemistry, but that all the principles that govern 

 chemical phenomena in inanimate matter are observed 

 in the processes peculiar to life. 



THE ORGANISM AS A MECHANISM UNDER INTERNAL 



CONTROL. 



The achievement of a certain limited, but still 

 very significant, control over the processes of 

 inanimate nature so as to make them proceed to 

 ends different from that which naturally they would 

 take, and, especially, in directions which are useful, 

 or which produce results otherwise only attainable 

 by the complex processes in the living organism, 



