42 



OF NUTRITION 



part is rejcded by tranfpiration, by fecretions, 

 and by other excretories ; and a fmall portion 

 only is retained for the nourifhment and expan- 

 fion of the parts. It is extremely probable, that, 

 in the bodies of animals and of vegetables, a fe~ 

 paration is made between the brute particles of 

 the aliment and the organic ; that the former are 

 carried off by the methods juft mentioned ; that 

 nothing but the organic particles remain ; and 

 that they are diftributed, by means of fome active 

 power, to the different parts, in a proportion fo 

 exa£t, that neither more nor fewer are applied 

 than anfwer the purpofes of nutrition, and of an 

 equal growth and expanfion. 



As to the fecond queftion. What is the nature 

 of that active power, which enables the organic 

 matter to penetrate and combine WMth the inter- 

 nal mould I It is apparent, from the preceding 

 chapter, that powers exift in Nature, like that of 

 gravity, which affedt the moft internal parts of 

 matter, without having the fmalleft relation to 

 its external qualities. Thefe powers, as former- 

 ly obferved, are beyond the reach of our fenfes ; 

 becaufe their adion is exerted upon the intimate 

 ftrudlure of bodies. It is evident, therefore, that 

 we can never obtain a clear idea of them, nor 

 of their mode of ading. Their exiftence, how- 

 ever, is not lefs certain, than that, by means of 

 them, moft natural effeds are produced, efpe- 

 cially thofe of nutrition and expanfion, which 

 niuft be owing to a caufe that penetrates the 



mofi: 



