58 ORIGIN AND ACTION OF HUMUS. 



in our laboratories, formic acid, oxalic acid, urea, 

 and the crystalline substances existing in the liquid 

 of the allantois of the cow, all products, it is said, 

 of the vital principle. We see, therefore, that this 

 mysterious principle has many relations in common 

 with chemical forces, and that the latter can indeed 

 replace it. What these relations are, it remains 

 for physiologists to investigate. Truly it would be 

 extraordinary, if this vital principle, which uses 

 everything for its own purposes, had allotted no 

 share to chemical forces, which stand so freely at 

 its disposal. We shall obtain that which is attain- 

 able in a rational inquiry into nature, if we sepa- 

 rate the actions belonging to chemical powers, from 

 those which are subordinate to other influences. 

 But the expression " vital principle " must, in the 

 meantime, be considered as of equal value with the 

 terms specific or dynamic in medicine : everything 

 is specific which we cannot explain, and dynamic is 

 the explanation of all which we do not understand. 

 Transformations of existing compounds are 

 constantly taking place during the whole life of a 

 plant, in consequence of which, and as the results 

 of these transformations, there are produced gaseous 

 matters which are excreted by the leaves and blos- 

 soms, solid excrements deposited in the bark, and 

 fluid soluble substances which are eliminated by the 

 roots. Such secretions are most abundant imme- 

 diately before the formation and during the continu- 

 ance of the blossoms; they diminish after the deve- 



