220 THE INDUCTIONS OF BIOLOGY. 



expends in any shape, is the correlate and equivalent of a 

 power that was taken into it from without." Motion, 

 sensible or insensible, generated by an organism, is insensible 

 motion which was absorbed in producing certain chemical 

 compounds appropriated by the organism under the form of 

 food. As much energy as was required to raise the elements 

 of these complex atoms to their state of unstable equilibrium, 

 is given out in their falls to a state of stable equilibrium; 

 and having fallen to a state of stable equilibrium they can 

 give out no further energy, but have to be got rid o*f as inert 

 and useless. It is an inevitable corollary " from the per- 

 sistence of force, that each portion of mechanical or other 

 energy which an organism exerts, implies the transforma- 

 tion of as much organic matter as contained this energy in 

 a latent state ; " and that this organic matter in yielding 

 up its latent energy, loses its value for the purposes of life, 

 and becomes waste matter needing to be excreted. The loss 

 of these complex unstable substances must hence be pro- 

 portionate to the quantity of expended force. Here, then, 

 is the rationale of certain general facts lately indicated. 

 Plants do not waste to any considerable degree, for the obvi- 

 ous reason that the sensible and insensible motions they 

 generate are inconsiderable. Between the small waste, small 

 activity, and low temperature of the inferior animals, the 

 relation is similarly one admitting of a priori establishment. 

 Conversely, the rapid waste of energetic, hot-blooded animals 

 might be foreseen with equal certainty. And not less mani- 

 festly necessary is the variation in waste which, in the same 

 organism, attends the variation in the heat and mechanical 

 motion produced." 



Between the activity of a special part and the waste of 

 that part, a like relation may be deductively inferred ; though 

 it cannot be inferred that this relation is equally definite. 

 Were the activity of every organ quite independent of the 

 activities of other organs, we might expect to trace out this 

 relation distinctly; but since increased activity in any organ 



