THE RELATION OF LIFE TO OTHER FORCES. 727 



descent of so much muscular substance to inorganic or less complex 

 organic shape; in other words, that the immediate fuel which an animal 

 requires for the production of force is derived from its own substance; 

 and that the food taken must first be appropriated by, and enter into 

 the very formation of living tissue before its latent force can be trans- 

 formed and manifested as vital power. And here, it might be said, is a 

 great distinction between a living structure and a simply mechanical 

 arrangement such as that which has been used for comparison; the fuel 

 which is analogous to the food of a plant or animal does not, as in the 

 case of the latter, first form part of the machine which transforms its 

 latent energy into another variety of power. 



We are not, at present, in a position to deny that this is a real and 

 great distinction between the two cases; but modern investigations in 

 more than one direction lead to the belief that we must hesitate before 

 allowing such a difference to be an universal or essential one. The 

 experiments referred to seem conclusive in regard to the production of 

 muscular power in greater amount than can be accounted for by the 

 products of muscular waste excreted; and it may be said with justice 

 that there is no intrinsic improbability in the supposed occurrence of 

 transformation of force, apart from equivalent nutrition and subsequent 

 destruction of the transforming agent. Argument from analogy, in- 

 deed, would be in favor of the more recent theory as the likelier of the 

 two. 



Whatever may be the result of investigations concerning the relation 

 of waste of living tissue to the production of power, there can be no 

 doubt, of course, that the changes in any part which is the seat of vital 

 action must be considerable, not only from what may be called t( wear 

 and tear/' but, also, on account of the great instability of all organized 

 structures. Between such waste as this, however, and that of an inor- 

 ganic machine there is only the difference in degree, arising necessarily 

 from diversity of structure, of elementary arrangement, and so forth. 

 But the repair in the two cases is different. The capability of recon- 

 struction in a living body is an inherent quality like that which causes 

 growth in a special shape or to a certain degree. At present we know 

 nothing really of its nature, and we are therefore compelled to express 

 the fact of its existence by such terms as "inherent power," "individ- 

 ual endowment," and the like, and wait for more facts which may ulti- 

 mately explain it. This special quality is not indeed one of living things 

 alone. The repair of a crystal in definite shape is equally an " individ- 

 ual endowment," or ef inherent peculiarity," of the nature of which we 

 are equally ignorant. In the case, however, of an inorganic machine 

 there is nothing of the sort, not even as in a crystal. Faults of structure 

 must be repaired by some means entirely from without. And as our 

 Tiotion of a living being, say a horse, would be entirely altered if flaws 



