Th HIS TORY of PN SECT s: 
thoroughly of thofe parts, which were firft ob- 
vious to me, Neither need I be uneafy, if I 
have delineated one part fomewhat larger, and 
* the other fomewhat lefs; the microfcope not 
admitting of greater accuracy: and indeed this 
avails nothing in our attempts to inculcate a 
‘knowledge of the fubjec, fick fome particular 
points may be more diftinétly underftood, if on 
that occafion, the parts are exhibited a little 
larger than the life. 
The beft manner of diffe&ting the Snail is, 
the fhell Tab. IV. fig. 11.2, being pulled off, 
to begin at the verge of the body, fig. 1. e; 
which alfo fhould be cut off from the left fide, 
with a fine pair of {ciffors ; in the doing this, 
taking care not to pierce the apertures g, fituated 
on its right f, thefe ftill remaining unhurt, the 
verge is to be feparated from the body, which 
vifibly adheres to it below ; for otherwife, unlefs 
thefe apertures be carefully avoided, the outlet 
of the inteftines, and the paflage of the alkaline 
bag, willbe equally injured: 
In this management, what fir meets the 
eye, isthe skin of the fubjacent body, which is 
concealed by the upper and under part of the 
verge, or a membranaceous fubftance, as with 
a covering, being much more delicate about 
that place, and of a whitith or palith colour, 
and compofed of oblong mufcular fibres. If 
you have nicely feparated this part of the inter- 
nal skin, you will fee the tranfverfe mufcles 
lying under it; which, though not altogether 
colourlefs, are in fome degree tranfparent ; and 
on both fides, in the foft or bending part of the 
belly, there will be obferved certain mufcles 
refembling a faw, which ftretch their tendons 
above the peritoneum ; but the fmall mutcle, 
running, tran{verly, is fituated above the perito- 
num, under which it lies. All thefe mufcles 
ferve to prefs the body inwards, and to move 
forwards the contents of the inteftines, and of 
the {permatic veffels. 
But if after this the verge, together with 
its membranaceous parts, be drawn backwards 
over the bending of the body, and then cut off 
from the place where it adheres, then imme- 
diately appear the veins, Tab. V. fig. iv. a, 
which run beneath toward the verge 4, and the 
heart c, with its auricle d, and the vena cava jatt 
dawning out of it ; together with the various 
cavities, in which the air is moved, and fome 
other {mall parts befide, fuch as the alkaline 
bag e, and its duct lying next to the inteftine, 
the inteftinum reétum / itfelf, the liver, and 
- certain parts belonging to the {permatic veftels. 
Some of thefe I fhall now defcribe in their 
order, and of the others afterwards in their 
place. Firft, of the heart. 
The heart is fituate in the middle of the 
Snail’s body, near the extremity of the arch 
of the verge, which furrounds the whole bo- 
dy; and at that place, a little to the left, in 
the bending of the body, by reafon of the 
thinnefs of the inteftine membranes, which 
are perfectly tranfparent, Tab. IV. fig. 1. /, it 
is difcerned moving, It is included in an ex- 
53 
tremely thin bag or pericardium, in whofe 
cavity there is ample abundance of watery 
moifture, as clear as the pureft chryftal. The 
pericardium being diffected, immediately ap- 
pears the beating heart, Tab. V. tieity.\"G, 
with its auricle d; which, being of a mem- 
branaceous and exceeding delicate texture, 
is feen to be interwove within, with divers 
as well flefhy as membranaceous fibres, in the 
fame manner as is feen in the auricles of the 
heart of a man, and other animals. The 
heart itfelf is of a flefhy fubftance, and of a 
pale reddifh colour, exhibiting a mufcle, which 
for the fpace of a day will continue wafting 
away into water, and yet not be cleared from 
all its blood. The external fuperficies of the 
heart is fmooth, and it is fhaped like a pear; 
but the internal parts are uneven, with feveral 
flefhy columns, hairs, and fibres, much the 
_fame as we obferve in the hearts of men and 
brutes: hence it is that the heart may be 
eafily diftinguifhed by the many finufes and 
angles in. it, and it is very fibrous. At its 
entrance, near the auricle, there adhere two 
little femi-lunar valves c, which ferve to hinder 
the blood from returning into the auricle. 
But as there is only one auricle to the heart, 
fo is it only found in one cavity ; and agreea- 
bly to this, there are alfo found two kinds of 
veflels there, namely, the veins and arteries. 
The veins, above the auricle d of the heart, 
are confpicuous without much pains, and in 
particular the vena cava may be obvioufly feen; 
out of which others, juft {pringing forth, are 
interwoven amongft one another after a fur- 
prifing manner, and form an elegant kind of 
net-work. The arteries are not difcovered 
without greater difficulty, nor can they ever 
be feen, but at the firft opening of the body. 
The beginning of the aorta, or great artery, 
is about that place without the belly, where 
the heart is united to the calcarious bage; and 
the great artery derives its origin from the 
cone, or more acute extremity of the heart, 
and is a little dilated, at its very beginning, as 
is common in fifhes; immediately from this 
part it difperfes its ramifications every way, 
both through the internal parts of the body, 
and outwardly among the membranes, equally 
backward to the {pire, and forward; firft, in- 
deed, refpecting thofe parts it borders upon, 
namely, the calcarious bag e, the inteftines, the 
liver, the {tomach, and the fpermatick veffels ; 
then immediately proceeding to the coat in- 
vefting the liver, and then to the mutcles, 
nerves, and little glands of the skin. I have 
delineated 4 fome of the more remarkable. ra- 
mifications, only with their divifions, and have 
marked the reft of its body, and its fpiral 
fhape, with points 2/77, that the fituation of 
thefe parts might thence be underftood. 
The blood contained in the heart, and its 
arteries, appears of a whitifh colour, inclining 
fomething to blue; and hence it differs very 
much from that of men and brutes; for the 
P | blood 
