16 THE PROGRESS AND SPIRIT OP 



impugn the doctrine of vitality, both in animal and vegetable 

 life, as a distinct force or power ; and to resolve its alleged 

 functions, whether of organisation, maintenance, or reproduc- 

 tion, into those same physical forces which act on the inor- 

 ganic matter of the world around us. That this is true to a 

 certain extent cannot indeed be doubted. That heat and 

 light, and more especially the former, are intimately con- 

 cerned in all the phenomena of vital organisation, is a fact 

 familiar to us from a thousand examples. The researches of 

 Liebig and others have shown how very closely chemical 

 processes are engaged even under the strict law of definite 

 proportions in all the great processes belonging to animal 

 life, assimilation, secretion, respiration, animal heat, &c. ; 

 while the discoveries of Matteucci and Du Bois Raymond 

 have demonstrated the curious and exquisitely subtle rela- 

 tions which exist between electricity and the nervous and 

 muscular functions ; not indeed proving the identity of elec- 

 tricity with the nervous element of force, but countenancing 

 this view beyond all prior expectation. 



In thus discussing the relation of the physical and vital 

 forces as applied especially to man, we continually approach 

 that line, hard indeed to discriminate or define, which 

 separates the mere vital or automatic acts from the proper 

 functions of mind, consciousness, thought, feeling, and voli- 

 tion. On this debatable land we encounter at once the old 

 questions, so long the subject of philosophical speculation, 

 and destined, as far as we can see, ever so to remain. Human 

 science on this point is as feeble as it was two thousand years 

 ago, and beset by exactly the same difficulties. We have 

 just been speaking of forces which are co-related and measur- 

 able in their effects. We come here to powers and functions 

 wholly incommensurable either with material qualities or 

 physical forces ; yet so linked with both under the present 

 conditions of existence, that not even personal consciousness, 



