SECT. III. EXTRACT. 6 



parts of fluid yielded 10 of extract. And in a simi- 

 lar experiment upon mould taken from a well cul- 

 tivated corn-field, 10,OOO parts of fluid yielded four 

 parts of extract.* Such was the result in these 

 particular cases* 



But the quantity of extract that may be separated 

 from pure mould formed by nature upon the sur- 

 face of the globe is not in general very consider- 

 able. After 13 decoctions, all that could be separated 

 from mould of this sort was about T V of its weight ; 

 and yet this seems to be more than sufficient for the 

 purposes of vegetation : for a mould containing this 

 quantity was found by experiment to be less fertile, 

 at least for Peas and Beans, than a mould that con- 

 tained only one half or two thirds the quantity.^ 



But if the quantity of extract must not be too 

 much, neither must it be too little. Plants that 

 were put to vegetate in mould deprived of its ex- 

 tract, as far as repeated decoctions could deprive it, 

 were found to be much less vigorous and luxuriant 

 than plants vegetating in mould not deprived of its 

 extract : and yet the only perceptible difference 

 between them is, that the former can imbibe and 

 retain a much greater quantity of water than the 

 latter.;}: 



From this last experiment, as well as from theConsti 

 great proportion in which it exists in the living viable 

 plant, it evidently follows that extract constitutes a [^n n " 



nitrogen e. 



* Sur la Veg. chap. v. sect. ii. f Ibid. J Ibid. 

 F 2 



