THE ACTIONS OF FORCES ON ORGANIC MATTER. 35 



equally remains true, that these changes are maintained by 

 its instrumentality. Whether the oxygen absorbed and 

 diffused through the system, effects a direct oxidation of the 

 organic colloids which it permeates ; or whether it first leads 

 to the formation of simpler and more oxidized compounds, 

 that are afterwards further oxidized and reduced to still 

 simpler forms ; matters not, in so far as the general result is 

 concerned. In any case it holds good, that the substances 

 of which the animal body is built up, enter it in a but 

 slightly oxidized and highly unstable state ; while the great 

 mass of them leave it in a fully oxidized and stable state. 

 It follows, therefore, that whatever the special changes gone 

 through, the general process is a falling from a state of un- 

 stable chemical equilibrium, to a state of stable chemical 

 equilibrium. Whether this process be direct or indirect, 

 the total molecular re-arrangement and the total motion 

 given out in effecting it, must be the same. 



§ 15. There is another species of re-distribution among 

 the component units of organisms, which is not immediately 

 effected by the aflanities of the units concerned, but is me- 

 diately effected by other affinities ; a,nd there is reason to 

 think that the re-distribution thus caused, is important in 

 amount, if not indeed the most important. In ordinary cases 

 of chemical action, the two or more substances concerned, 

 themselves undergo changes of molecular arrangement; and 

 the changes are confined to the substances themselves. But 

 there are other cases in which the chemical action going on, 

 does not end with the substances at first concerned ; but sets 

 going chemical actions, or changes of molecular arrangement, 

 among surrounding substances that would else remain qui- 

 escent. And there are yet further cases in which mere 

 contact with a substance that is itself quiescent, will cause 

 other substances to undergo rapid metamorphoses. In 



what we call fermentation, the first species of this communi- 

 cated chemical action is exemplified. One part of yeast, 



