56 LIFE AND ORGANISATION. 



mutual convertibility ; that their forces, however altered in 

 respect of action, are never really lost or lessened ; that they 

 are the efficient energy, not solely in the greater and more 

 obvious phenomena of the material world, but equally so in 

 the most minute molecular actions to which matter is subject. 

 We can modify, by human powers and machinery, the aspects 

 of force and its actions upon matter. We can never either 

 create or annihilate it. These conclusions, at the utmost but 

 vaguely and partially surmised before, have now acquired 

 certainty enough to give them place among the great general 

 laws of nature ; and experimental science is every day bring- 

 ing fresh facts to their proof and illustration. Whether the 

 term of ' Co-relation of Forces,' provisionally applied by 

 Mr. Grrove to describe what is our present knowledge, may 

 not hereafter merge in the single phrase and conception of 

 Force, as contradistinguished from the matter on which it 

 acts, is a point open to future determination. Mutual con- 

 vertibility is closely akin to unity, if not an actual expression 

 of it. Much that is of the deepest interest to philosophy 

 hangs upon the solution of this problem ; involving, as will be 

 seen, all the relations of matter to that mighty influence 

 which has been destined to mould it into form, activity, and 

 even into life itself. 



It is here, in fact, that we find ourselves in the very heart 

 of the question to which we have just alluded as still the 

 subject of serious controversy ; viz., whether there be really 

 any separate Vital Principle ; a positive and independent 

 power, giving organisation and life to certain combinations 

 of matter ? Or whether the simple vital phenomena may not 

 be referred, as effects, to those great physical powers, which 

 we see acting so incessantly on all matter in the universe ; 

 and the actual influence of which upon the vital functions is 

 obvious at every moment of existence ? 



Each of these views has found zealous advocates, and been 



