Of Vegetation. 343 
Dr. Keith in his account of animal fecre- 
lion, page 49, obferves, that where nature 
Intends to feparate a vifcid matter from the 
blood, fhe contrives very much to retard 
its motion, whereby the inteftine motion of 
the blood being allayed, its particles can the 
better coalefce in order to form the vifcid 
fecretion. And Dr. Grew , before him, oh- 
ferved an inftance of the fame contrivance 
in vegetables where a fecretion is intended, 
that is to compofe a hard fubftance, viz. in 
the kernel or feed of hard ftone fruits, 
which does not immediately adhere to, and 
grow from the upper part of the ftone^ 
which would be the fhorteft and neareft 
way to convey nourifhment to it 5 but the 
jingle umbilical veftel, by which the kernel 
is nouriihed, fetches a compafs round the 
concave of the ftone, and then enters the 
kernel near its cone, by which artifice this 
veftel being much prolonged, the motion of 
the fap is thereby retarded, and a vifcid nu- 
triment conveyed to the feed, which turns 
to hard fubftance. 
The like artifice of nature we may obferve 
in the long capillary fibrous veffels which 
lie between the green hull, and the hard 
fhell of the Walnut, which are analogous 
Z 4 to 
