[ 44 ° ] 
matter are folid, tho’ never ib minute, and are car- 
ried with the fluids of the animal to the membrane, 
now ready to receive them into the dubts of its 
glands ; and are thence thrown into fuch order in 
the cellules of the external furface, as to acquire a 
ftrubture no leis Arm, in proportion, than bricks 
laid on one another ; and as capable of bearing any 
fair prefiure, as a well-built arch. 
When they are thus hardened and complete, they 
may be render'd as foft and flexible, by being mace- 
rated in vinegar, as if the flielly particles had never 
been placed upon them. And this is not, becaufe 
the matter is. quite diflolved ; for a vegetable acid is 
not capable of making a total di Ablution of it ; but 
the minute angles are deflroy’d, and the particles 
(which were before fix'd like wedges to each other, 
to which they were inevitably guided in the fecretion 
by the very ftrudture of the receiving cellules of the 
membrane) are become round, by the deftrubtion of 
their angles, and admit of being roll’d in fome mea- 
fure upon one another, fo as in the whole to yield 
to the natural flexibility of the membrane. 
I am, with great refpedt and friendfhip, 
Your moft humble fervant , 
James Parfons. 
LXXIV. 
