376 MAUEY ON SLEEP AND DREAMS. 



life, destined to the restoration of those vital powers 

 which are exhausted or impaired by the very act of 

 living. Here we are on firmer ground. Whatever 

 anomalies may present themselves, it is certain that 

 sleep fulfils, and is intended to fulfil, this great office 

 of our nature. That which is taught us by universal 

 experience is amply confirmed and illustrated by phy- 

 siological inquiry. The wonderful power, to which 

 various names have been given, but which may best, 

 and most simply, be described as nerve-force an ele- 

 ment acting through the brain and nervous system in 

 all the phenomena of sensation, of motions voluntary 

 and reflex, and of every function essential to animal 

 life is now so far subjected to research, that even the 

 velocity of its transmission through the nerves of sen- 

 sation and voluntary motion has been approximately 

 ascertained. This eminent discovery, and the subtle 

 methods by which it was accomplished, warrant the 

 hope that further research may accomplish a similar 

 numerical expression for the amount or quantity of 

 the nerve-force at any given time a matter bearing 

 still more directly on the subject before us. If, in- 

 deed, this were attained, it would be only formulating 

 in figures a fact of the reality of which we are well 

 assured. We know that the force in question, thus 

 acting through the total nervous system of the body, is 

 the product (secretion we may venture to call it) of a 

 peculiar organised tissue that it varies hr amount in 

 different individuals, and in the same individual at dif- 

 ferent times that it is exhausted, more or less, by the 

 vital actions, bodily and mental, to which it ministers 



