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XXIV. Oljettions againft the Perceptrorty of Plants, fo far as is evinced 
by their external Motions, in Anfwer to Dr. Peretoal’s Memoir in the 
Manchefier Tranfaëtions. By Robert Townfon, Efq. F. R, S. Edinb. 
Read Dec. 4, 1792. 
OW A et we pa | he i in our expectations of ex- 
^t > the limits of human knowledge, we cannot avoid 
perceiving that there are Howtidarien gh it never can exceed. 
Thefe boundaries are the limited faculties of the human mind, 
which, though fully fufficient to anfwer all the purpofes of com- 
mon life, are an infuperable barrier to the enquiries of fpeculative 
men. None feel more the truth of this obfervation, than thofe 
engaged in phyfiological enquiries; the operations of nature being 
fo complicated, and at the fame time carried on in fo fecret a 
manner, as to keep us ignorant of the moft common phæ- 
nomena. 
If phyfiologifts have been unfuccefsful in many of their enqui- 
ries into the animal ceconomy, they have been ftill more fo with 
refpect to vegetables: for how little do we know at this day of the 
courfe‘of their fluids, and of the power by which they are moved? 
Are we not in the vegetable kingdom where we were near two cen- 
turies ago in the animal, when the great Harvey withdrew the veil ? 
Mm2 The 
