84 USES OF THE 



in professedly chemical works, is carried to a 

 greater length than I have thought necessary 

 in a physiological one. See Thomson s Che- 

 mistry^ v. 4, and Willdenozvs Principles of 

 Botany^ 229. We must ever keep in mind, 

 as we explore it, that our anatomical instru- 

 ments are not more inadequate to dissect the 

 organs of a scarcely distinguishable insect, 

 than our experiments are to investigate the 

 fine chemistry of Nature, over which the 

 living principle presides. 



Before we take leave of the secreted fluids 

 of vegetables, a few more remarks upon their 

 direct utility to the plants themselves may 

 not be superfluous. Malpighi first suggested 

 that these secretions might nourish the plant, 

 and our latest inquiries confirm the sugges- 

 tion. Du Hamel compares them to the 

 blood of animals, and so does Darwin. But 

 the analogy seems more plain between the 

 sap, as being nearly uniform in all plants, 

 and the ammal blood, as in that particular 

 they accord, while the secreted fluids are so 

 very various. Mr. Knight's theory confirms 

 this analogy, at the same time that it esta- 

 bhshes the opinion of Malpighi. The sup 



