ADAPTATION 203 



so-called enzymes or ferments. These are known to exist in 

 the most different forms even in the inorganic world. They 

 are simply chemical compounds, of specific types, that 

 bring about chemical reactions between two other chemical 

 materials, which in their absence would either not go on 

 at all or would go on very slowly. We cannot enter here 

 into the much disputed chemical theory of what is called 

 " catalysis " : we can only say that there is no objection to 

 our regarding almost all metabolic processes inside the 

 organism as due to the intervention of ferments or cata- 

 lytic materials, and that the only difference between 

 inorganic and organic ferments is the very complicated 

 character of the latter and the very high degree of their 

 specification. 



Such a statement, of course, does not say that all 

 metabolism has proved to be of a chemical nature: the 

 action of the ferment when produced is chemical, but we 

 do not know at all how the ferment is produced ; we only 

 know that a high degree of active regulation is shown in 

 this production. In fact, it has been proved in some cases, 

 and probably will be proved in a great many more in the 

 near future, that all metabolic ferments, whether they 

 promote oxidation or assimilation proper or chemical decom- 

 position, are produced in a regulatory manner with regard 

 to the specific compound to be dissociated or to be built 

 up. In this way the whole field of metabolism is really 

 covered by " regulations." Are they real " secondary ' 

 ones? Of course the regulatory correspondence applies to 

 the process of secretion in the first place, not to the actual 

 formation of the ferment inside the cell. The correspondence 

 as to secretion, no doubt, is of the primary type ; is there 



