instrument the determinate bulk of the parts of the _medium_ that conveys
the pulse of light, since we find that there is not less accurateness shewn
in the Figure and polish of those exceedingly minute lenticular surfaces,
then in those more large and conspicuous surfaces of our own eyes. And yet
can I not doubt, but that there is a determinate bulk of those parts, since
I find them unable to enter between the parts of Mercury, which being in
motion, must necessarily have pores, as I shall elsewhere shew, and here
pass by, as being a digression.

As concerning the horns FF, the feelers or smellers, GG, the _Probascis_
HH, and I, the hairs and brisles, KK, I shall indeavour to describe in the
42. _Observation_.

* * * * *

Observ. XL. _Of the Teeth of a _Snail_._

I have little more to add of the Teeth of a Snail, besides the Picture of
it, which is represented in the first _Figure_ of the 25. _Scheme_, save
that his bended body, ABCDEF, which seem'd fashioned very much like a row
of small teeth, orderly plac'd in the Gums, and looks as if it were divided
into several smaller and greater black teeth, was nothing but one small
bended hard bone, which was plac'd in the upper jaw of the mouth of a
House-Snail, with which I observ'd this very Snail to feed on the leaves of
a Rose-tree, and to bite out pretty large and half round bits, not unlike
the Figure of a (C) nor very much differing from it in bigness, the upper
part ABCD of this bone, I found to be much whiter, and to grow out of the
upper chap of the Snail, GGG, and not to be any thing neer so much creas'd
as the lower and blacker part of it HIIHKKH which was exactly shap'd like
teeth, the bone growing thinner, or tapering to an edge towards KKK. It
seem'd to have nine teeth, or prominent parts IK, IK, IF, &c. which were
join'd together by the thinner interpos'd parts of the bone. The Animal to
which these teeth belong, is a very _anomalous_ creature, and seems of a
kind quite distinct from any other terrestrial Animal or Insect, the
Anatomy whereof exceedingly differing from what has been hitherto given of
it I should have inserted, but that it will be more proper in another
place. I have never met with any kind of Animal whose teeth are all join'd
in one, save onely that I lately observ'd, that all the teeth of a
Rhinocerot, which grow on either side of its mouth, are join'd into one
large bone, the weight of one of which I found