48 
The ufe of the eye in the Snail, and the 
manner wherein it exercifes its vifual faculty, 
is a matter of great difficulty to inveftigate. 
The grey coat, Tab. IV. fig. vir. 464, which 
is the expanfion of the mutcle of the eye, and 
may be very much dilated and contracted, 
feems to me to move various ways; nay, that 
it ferves as a cover like our eye-lids: but the 
bignefs or {mallnefs of the pupil or foramen, ’ 
or aperture of the uvea, and in what manner 
it is contracted or dilated, as light and objects 
vary, I have not hitherto been able to ob- 
ferve, nay, I never yet faw the pupil of the 
eye in a Snail; nor fhould any wonder at this, 
if in the human eye, though fo big, the foramen 
or aperture of the pupil is no larger than a Pidge- 
on’s quill; what a {mall and fine aperture then 
muft the pupil have in this little point, and how 
few rays can pafs into it? however, I don’t doubt 
but the pupil is contra¢table and dilatable ; for 
I have obferved the ciliary duct there, by 
which, when the pupil’ is dilated, the eyes of 
the Snail can receive the humors, and collect 
external vifible objects, which, after paffing the 
humors, are afterwards received in the retina, 
placed underneath at the bottom of the uvea, 
by the optic nerve ; which is the caufe of vi- 
fion. Hence it may, perhaps, be juftly in- 
ferred, that the fight of the Snail muft of ne- 
a s “ee. 
Cc F 
Coe BA wks 
The BOOK of NATURE; or, 
ceffity be very dim ; for we ourfelves do not 
fee clearly in the day-time, if we go into a 
houfe out of the open air; the pupil of our 
eye is by that contracted in fuch a manner, that 
fewer rays of light are collected in our eye. 
Nay, perhaps the Snail does not receive the 
rays of light and objects but at a diftance, 
and only fees them through a cloud as it were, 
and cannot diftinétly know them near at hand ; 
as the man born blind is faid in the gofpel to 
have feen men like walking trees: I could not 
at leaft hitherto obferve, that the Snail fees well 
the things which are near it, notwithftanding 
all the attempts I*made for this purpofe. In 
the eye of the Mole I have likewife feen, even 
without a microfcope, the three humors before- 
mentioned, but they are there larger, and eafier 
to be diftinguifhed, though it is probable even 
this creature cannot. fee diftinctly under the 
earth. : 
I fhall conclude this chapter with admiring 
the ftrange and remarkable things which I have 
fhewn in it, from the cleareft experiments, 
and which feem to me the more admirable, 
the more diligently I meditate upon them: 
God truly every where fhews that he is worthy 
of the moft humble adoration in all his works, 
which we may and ought diligently to fearch 
into, but can never fully comprehend. 
IT. 
Of rhe lips, mouth, teeth, tongue, palate, efophagus or gullet, and certain 
) mufcles of the Snail, 
ET WEEN the two lower horns of 
this creature are feen its lips on the out- 
fide, Tab. IV. fig. 1. c, and whilft the Snail 
draws them afunder, the intermediate skin is 
obferved to be fet like the edge of a faw, as 
it were with prominent little teeth. This can 
never be feen better than while theSnail is eating, 
or when the mouth, palate, and jaws, together 
with theoutward skin, are taken offand diflected. 
In this cafe, Tab. V. fig. 1. the teeth 6 imme- 
diately appear behind that skin 2; and in a 
boiled Snail they are rendered very vifible, 
Tab. IV. fig. 1v.r, becaufe the skin and lips be- 
come thus contracted. Thefe teeth are con- 
nected by a certain horny concretion; Tab. V. 
fig. 11. 4, the teeth themfelves being all made 
of a horny fubftance ; and they are of a light 
red colour. Since therefore all thefe teeth are 
connected one with the other, they ought to be 
efteemed, in fome meafure, as one tooth. They 
. are eight 6 in number, and fome are larger and 
more prominent than others, as appears by the 
microfcope. This little part is made in the 
form of a circle c, its convex fide lying on the 
infide upwards, towards the fkin, to which 
it is ftrongly connected; but its toothed 
concave fide, with which it bites, is di- 
rected on the outfide. In the middle of the 
convex furface of this tooth, there is a {mall 
furrow, in which fome of the mufcles that 
move the whole are fixed. The tooth after- 
wards becoming infenfibly membranaceous, ex- 
pands itfelf like a pretty large pyramid or bod- 
kin, fig. 1.¢, and in that form conftitutes a 
great part of the palate, which, on each fide 
of this expanfion, is beautifully variegated with 
{mall ruddy points: thefe here and there fhew 
little parts that are fomewhat hard, and of a 
horny fubftance, and ferve to prevent the in- 
ward part of the body from being wounded 
or hurt, in cafe the Snail fhould at any time 
{wallow any thing too hard or rough. But this 
cannot be feen, unlefs the inward parts of the 
mouth be firft diflected, and taken out fepa- 
rately. Then two fimall, narrow holes or aper- 
tures d are feen on the upper and under part in 
the palate, which convey the faliva out of its 
duéts into the mouth. 
In the lower part of the mouth, or where 
our lower jaw is placed, are, in the Snail on the 
fore part, two {mall flefhy fubftances e, which 
may be called the inward lips, for they con- 
tribute greatly to direét the paflage of the food; 
that is, to carry it towards the gullet, and thruft 
it down. Behind thefe, a certain very delicate 
and tender membranous crooked cartilage ak 
; ent 
