72S HANDBOOK OF PHYSIOLOGY. 



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 absorbing and using part of its fuel as mat- 

 ter wherewith to repair any ordinary 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 justice of this criticism depends on the manner in which the 

 word "vital" is used. If by it we intend to express an idea of some- 

 thing which arises in a totally different manner from other forces some- 

 thing which, we know not how, depends on a special innate quality of 

 living beings, and owns no dependence on ordinary physical force, but is 

 simply stimulated by it, and has no correlation with it then, indeed, it 

 would be just to say that the whole matter is merely shelved if we. retain 

 the term "vital force." 



But if a distinct correlation be recognized between ordinary physical 

 force and that which in various shapes is manifested by living beings; if 

 it be granted that every act say, for example, of a brain or muscle is 

 the exactly correlated expression of a certain quantity of force latent in 

 the food with which an animal is nourished; and that the force pro- 

 duced either in the shape of thought or movement is but the transformed 

 expression of external force, and can no more originate in a living organ 

 without supplies of force from without, than can that organ itself be 

 formed or nourished without supplies of matter; if these facts be recog- 

 nized, then the term used in speaking of the powers exercised by a liv- 

 ing being is not of very much consequence. We have as much right to 

 use the term " vital " as the words galvanic and chemical. All alike are 

 but the expressions of our ignorance concerning the nature of that power 

 of which all that we call " forces" are various manifestations. The dif- 

 ference is in the apparatus by which the force is transformed. 



It is with this meaning that, for the present, the term " vital force " 

 may still be retained when we wish shortly to name that combination of 

 energies which we call life. For, exult as we may at the discovery of 

 the transformation of physical force into vital action, we must acknowl- 

 edge not only that, with the exception of some slight details, we are 

 utterly ignorant of the process by which the transformation is effected; 

 but, as well, that the result is in many ways altogether different from 

 that of any other force with which we are acquainted. 



It is impossible to define in what respects, exactly, vital force differs 

 from any other. For while some of its manifestations are identical with 

 ordinary physical force, others have no parallel whatsoever. And it is 

 this mixed nature which has hitherto baffled all attempts to define life, 

 and, like a Will-o'-the-wisp, has led us floundering on through one definition 



