II OF THE NATURAL HISTORY SCIENCES 43 



The particle of gold falls to the bottom and 

 rests — the particle of dead protein decomposes and 

 disappears — it also rests: but the living protein 

 mass neither tends to exhaustion of its forces nor 

 to any permanency of form, but is essentially dis- 

 tinguished as a disturber of equilibrium so far as 

 force is concerned, — as undergoing continual meta- 

 morphosis and change, in point of form. 



Tendency to equilibrium of force and to per- 

 manency of form, then, are the characters of that 

 portion of the universe which does not live — the 

 domain of the chemist and physicist. 



Tendency to disturb existing equilibrium — to 

 take on forms which succeed one another in defi- 

 nite cycles — is the character of the living world. 



AVhat is the cause of this wonderful difference 

 between the dead particle and the living particle 

 of matter appearing in other respects identical? 

 that difference to which we give the name of 

 Life? 



I, for one, cannot tell you. It may be that, by 

 and by, philosophers will discover some higher 

 laws of which the facts of life are particular cases 

 — very possibly they will find out some bond be- 

 tween physico-chemical phgenomena on the one 

 hand, and vital phaenomena^ on the other. At 

 present, however, we assuredly know of none; 

 and I think we shall exercise a wise humility in 

 confessing that, for us at least, this successive 

 assumption of different states — (external condi- 



