P A R R 
with the nerves, and of the thoracic dud: with the venal 
blood. Fig. i, the aorta. Fig. 2, the vena cava. Fig. 
3, the cefophagus. Fig. 4, the brachial nerves. Fig. 5, 
the parotid glands. Fig. 6, the falivary canal. Fig. 7, 
the maxillary arteries and veins. Fig. 8, the feminal 
vefTels. Fig. 9, branch of lymphatic velfels of the pof- 
terior extremity. Fig. to, the epididimis. Fig. n,the 
canal dift'crens. Fig. 12, the pancreas. Fig. 13, the 
thoracic dud, or refervoir of the chyle. Fig. 14, the 
tranf'verfe apophyfis of the lumbar vertebrae. Fig. 15, 
lodgement of the kidneys. Fig. 16, mamellae of the kid¬ 
neys. Fig. 17, the ftomach, duodenum, and mefentery, 
with the external membrane removed, in order to exhibit 
the beautiful all'emblage of veins, arteries, and ladeal 
vefTels. The arteries are all injeded, to fhew the red 
blood; the veins blue; the nerves white; the ladeals 
grey. 
OF THE VISCERA. 
By vifcera, we underhand all the parts or organs, con¬ 
tained within the cavities or hollows of the fkeleton, or 
external frame of bone. Such are the contents of the 
head ; of the thorax or chef!; and of the abdomen or 
-belly. The parts proper to the firfl cavity, or head, are 
the brain, medulla oblongata, See. Thofe of the fecond, 
or clieft, are the lungs, and heart, &c. Thofe'of the 
third cavity, or abdomen, are the ftomach, inteftines, 
liver, fpleen, or milt, pancreas or fweet-bread, kidneys, 
ureters, and parts proper to generation. All thefe we 
ill a 11 deferibe in their refpedive order. 
Of the HEAD. 
Immediately within the fkull lies the dura mater , fo 
called from its texture, which is very firm ; and likewife 
to give origin to mod of the membranes throughout the 
body. It is the uppermoft- membrane peculiar to the 
brain, which it involves and covers on all parts; and be- 
lides the communication it has with the pericranium, it 
is tied to the pia mater, and to the brain itfelf, by the 
biood-veftels which penetrate the fkull, and are inferted 
in it, and pafs through it. This membrane is double, 
like the peritonaeum and pleura, and fends forth a pro¬ 
duction, which in man refembles a fickle, and is therefore 
called th eja/x. This membrane divides the upper part, 
or conical lubftance of the brain, into a right and left 
fide. Within its duplicature are feversl cavities, called 
the finufes of the dura mater , the longeft of which runs 
length-wife, and is divided into fev.eral branches, where¬ 
of two del'cend downward to the bottom of the occiput, 
and a third to the glundula pinealis. The piamater, which 
immediately involves the brain, and adheres clofe to it 
in- its, convolutions ana folds, is a very thin membrane, 
but of exquifite (enfe. It is furnifhed with an infinite 
number of arteries, which fpring from the carotid and 
cervical arteries ; and with veins from the jugulars ; all 
of which are very fmall, but finely interwoven ope .with 
another. Thefe two membranes are not only of ufe to 
cover and involve the brain, in order to preferve it, and 
to hold its delicate lubftance together, but alfo to fuftain 
the vefTels that enter into it. They are farther ufeful, as 
they make up the two innermoll coats which iheuth the 
fpinal marrow. 
The brain of a horfe is much lefs in proportion than 
that of a man; but iscompofedof a medullary lubftance, 
and has molt or all the parts which are dilcoverable in a 
human head. It is alfo divided into three parts, viz. the 
cerebrum, cerebellum, ai)d medulla oblongata. The 
cerebrum contains all that lubftance which lies .uppermolt 
in the head, and which is divided in half by the falx above 
delcribed. Its outlide is of an ulhy colour, and formed 
into leveral convolutions and windings, but not with Tuch 
vifible regularity as the cerebellum ; its infide is white, 
and therefore called the corpus callofum. The cerebellum 
is divided from the cerebrum by a produdtion of lire pia 
mater, which alfo affords a particular cover to all its.folds, 
Vol. Vi I. No. 422. 
I E R Y. 237 
which keep them feparate from each other. This is made 
up of four parts, whereof two are lateral, and two in the 
middle, (landing before and behind; they are fomewhat 
orbicular, and are called the proccjfes venniculares, from the 
refemblance they bear to worms. The medulla oblongata 
is the beginning of the fpinal marrow, as ftiewn in the 
Farriery Plate VI. It is of an uniform, white,.and com¬ 
pact, fubftance, harder than the brain or cerebellum. It 
rifes from fix roots, two of which fpring from that part 
of the brain called the corporaJlriata ; the other four rile 
lower and more backward. 
The rcte mirabile , which fupports the brain, is a curious- 
reticulation of biood-veftels, formed out of the fmall 
branches which fpring from the larger carotid arid cervi¬ 
cal arteries, having pafted through the fkull by proper- 
holes in the bones of the temples. Thefe vefTels are the 
more adapted to the nourifhment of the brain, by being 
thus interwoven one with another, as by that means the 
blood is longer retained, than if they obferved a lineal 
direction. The glandula pituitaria is the next tiling ob- 
fervable : towards the bottom of the brain it is enclofed 
within the membranes, and feated in a fmall cavity in the 
os cuneiforrr.e, or wedge-like bone, provided by nature 
for that purpofe. It has a conduit called the infundibulum, 
which conveys the excrementous matter of the brain into 
it ; and for that reafon moftanatomifts have believed there 
was a palfage from it to the nofe ; but late enquiries have 
difeovered two fmall dubts which it fends off to the jugu¬ 
lar veins ; whence fome are of opinion it is again mixed 
with the blood. 
Anatomifts have been fo much puzzled to find out 
proper refeuiblances for leveral parts of the brain, that 
they have diiliriguithed fome of them by the vulgar names 
of nates , or buttocks, and others by that of tejlcs, or 
ftones. Thefe confift of four orbicular eminences, which 
jut out from the medulla oblongata, or beginning of the 
fpinal marrow ; the two firft being the largeft, and the 
two other only appendages to them. The corpora Jlriala, 
fo called from their being (freaked or chamfered, are 
only the tw.o points or ends which proceed from the nates ; 
by thefe the medulla oblongata adheres to the brain ; and 
by the nates and teftes it adheres to the cerebellum. Be¬ 
tween the nates-is placed the gland called glandula pine, 
alis. Beiides the parts already delcribed, there are the 
fornix, and ie.ptum lucidum. The feptum lucidurn 
is only that portion which divides the ventricles ; and 
the fornix is a kind of vault or arch, which rifes between 
the brain and the medulla oblongata, and ferves to fup- 
port the upper part of the brain, that it may not prefs 
too hard upon the fubjacent parts. By means of this 
mod delicate organization the animal fpirits are elaborat¬ 
ed, and from hence conveyed into the nerves, which com¬ 
municate vigour and adtion to all parts of the'body. 
The eye9 tire the organs of vifion ; all outward obicdls 
being conveyed by them- to the common fenfory. They 
are of a convex globular figure, inclofed within their 
proper orbits. The eyelids ferve as a lafeguard to pre- 
ferve them from external injuries. They are compoled 
of the (kin, fleftiy paunicle, and mufcles, which are all 
wrought into an exquifite finenels : the inner membrane, 
which is very fmootli, that the eye may move.the more 
ealily under it, is a production of the pericranium ; the 
extremities or edges are very hard, partly to help their 
action, and partly that they may meet clofe together. 
The eye itfelf is compoled of three humours, and four 
tnnicles ; the firft of its tunicles is called adnata ; it riles 
from the pericranium, and is fpread all over the white of 
the eye, by which means it keeps it firm in its focket. 11 
is of exquifite fenfe, and very full of biood-veftels, which 
are perceivable at all times, but efpecially when the eye 
lias received any injury. The next, which is the firft of 
its proper coats, is called the fclerotica , from its hardnels. 
It riles from the dura mater, being opaque on its hind- 
part, but clear and tranlparent on its fore-part, from 
whence rt is called the cornea. The third is named cko- 
3 P ' roides , 
