THE RE- ACTIONS OF ORGANIC MATTER ON FORCES. 57 



arrangements, minute sensible motions so caused, may be ac- 

 cumulated into large sensible motions. There is, however, 

 no evidence to support this supposition. 



23. But the truths which it is here our business espe- 

 cially to note, are quite independent of hypotheses or inter- 

 pretations. It is sufficient for the ends we have in view, to 

 observe that organic matter does exhibit these several conspi- 

 cuous re-actions, when acted on by incident forces : it is not 

 requisite that we should know how these re-actions originate. 



In the last chapter were set forth the several modes in. 

 which incident forces cause re-distributions of organic mat- 

 ter ; and in this chapter have been set forth the several modes 

 in which is manifested the motion accompanying this re-dis- 

 tribution. There we contemplated under its several aspects, 

 the general fact, that in consequence of its extreme instability, 

 organic matter undergoes extensive molecular re-arrange- 

 ments, on very slight changes of conditions. And here we 

 have contemplated under its several aspects, the correlative 

 general fact, that during these extensive molecular re-arrange- 

 ments, there are necessarily evolved large amounts of force. 

 In the one case the atoms of which organic matter consists, 

 are regarded as changing from positions of unstable equi- 

 librium to positions of stable equilibrium ; and in the other 

 case they are regarded as giving out in their falls from 

 unstable to stable equilibrium, certain momenta momenta 

 that may be manifested as heat, light, electricity, nerve- 

 force or mechanical motion, according as the conditions 

 determine. 



I will add only that these evolutions of force are rigor- 

 ously dependent on these changes of matter. It is a corol- 

 lary from that primordial truth which, as we have seen, 

 underlies all other truths, (First Principles, Y6, 141,) 

 that whatever amount of power an organism expends in 

 any shape, is the correlate and equivalent of a power that 

 was taken into it from without. On the one hand, it 

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