320 HAND-BOOK OF PHYSIOLOGY. 



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 a universal or essential one. The experi- 

 ments 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, indeed, 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 "wear and 

 tear," but, also, on account of the great instability of all organized struc- 

 tures. Between such waste as this, however, and that of an inorganic 

 machine there is only the difference in' degree, arising necessarily from 

 diversity of structure, of elemental arrangement, and so forth. But the 

 repair in the two cases is different. The capability of reconstruction 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," "individual endowment," 

 and the like, and wait for more facts which may ultimately explain it. 

 This special quality is not indeed one of living things alone. The repair 

 of a crystal in definite shape is equally an "individual endowment," or 

 "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 notion of a living being, 

 say a horse, would be entirely altered if flaws in his composition were 

 repaired by external means only; so, in like manner, would our idea of the 

 nature of a steam-engine be completely changed had it the power of ab- 

 sorbing and using part of its fuel as matter wherewith to repair any ordi- 

 nary injury it might sustain. 



It is this ignorance of the nature of such an act as reconstruction 

 which causes it to be said, with apparent reason, that so long as the term 

 "vital force" is used, so long do we beg the question at issue What is 

 the nature of life? A little consideration, however, will show that the jus- 

 tice of this criticism depends on the manner in which the word ""vital" is 

 used. If by it we intend to express an idea of something which arises in 

 a totally different manner from other forces something which, we know 

 not how, depends on a special innate quality of living beings, and owns no 



