96 LIFE AND ORGANISATION. 



fulfillment to its numerous offices in the living economy? 

 Or must we look to some mysterious power existing here, 

 apart from matter and the forces acting on matter, as need- 

 ful to explain the phenomena, and particularly those which 

 connect the nervous system with consciousness and the 

 mental functions ? This question, like the analogous one as 

 to a Vital Principle, presses upon us almost as a necessity of 

 thought. As in so many other cases, language has sought to 

 evade the difficulty of solution by phrases more or less con- 

 venient for use, but which indicate no new or real knowledge 

 acquired. We employ the terms of nervous power, principle, 

 energy and element, nerve-force, innervation, &c., all pre- 

 ferable, doubtless, to the older phrase of nervous fluid ; but 

 preferable simply because less definite in their assumption 

 of meaning. 



To the question stated above, science has yet rendered no 

 certain answer ; but there are several presumptions favouring 

 the view that some physical agent analogous to, if not the 

 same as, the natural forces of which we have so often spoken 

 does directly minister to the functions of the nervous 

 system. One of these presumptions is founded on that con- 

 ception of quantity, which is forced upon us in every con- 

 sideration of nervous power, and is expressed equally by 

 excess or deficiency in amount. We exhaust Snergy by 

 action ; we augment it again by time and rest. Scarcely can 

 we name a function of life which does not include the fact of 

 a power inherent in it, thus varying in degree. Whether we 

 can apply the term intensity, as separate from quantity, is 

 more doubtful ; for though the distinction is valid as applied 

 to electrical action, it is not equally so as regards nervous 

 power. A much more cogent presumption to this effect is 

 that furnished by time as an element in the action through 

 nerves. This very interesting fact of a rate of motion, 

 already conjectured and vaguely estimated, has been recently 



