3 3 ^ 
inconvenience we may obferve, that nature 
has provided feveral Diaphragms, befides 
thofe at each knot, which are placed at 
fmail diftances acrofs the pith , thereby pre- 
venting its too great lateral dilatation. Thcfe 
are very plain to be feen in Walnut-tree 
fhoots 5 and the fame we may obferve in the 
pith of the branches of the fun-flower, and 
of feveral other plants 5 where tho*thefe Dia- 
phragms are not to be diftinguilhed while the 
pith is full and replete with moifture, yet 
when it drys up, they are often plain to be 
feen ; and it is further ohferved, that where 
the pith confiftsof diftincl: veficles, the fibres 
of thofe veficles are often found to run 
horizontally, whereby they can the better 
refift the too great lateral dilatation of the 
Ihoot. 
We may obferve that nature makes ufe of 
the fame artifice, in the growth of the feathers 
of Birds, which is very vifible in the great 
pinion feathers of the wing, the fmaller and 
upper part of which is extended by a fpongy 
pith, but the lower and bigger quill part, by 
a feries of large veficles, which when replete 
with dilating moiflure do extend the quill, 
but when the quill is full grown, thefe 
' -veficles 
4 
