tight side, it is called sinus venosus sinister. 
How-efer,the bag and appendix have but one 
common cavity, and therefore may still be 
both comprehended under the common name 
of left s auricle. In men the small portion 
may likewise be named the appendix of the 
left auricle ; but in other animals the case is 
l different. 
This small portion or appendix of the left 
I auricle is of a different structure from that 
of the bag or large portion. Exteriorly it 
resembles a small oblong bag bent different 
ways, and indented quite round the edges. 
Interiorly it is like the inside of the right au- 
ricle. The whole common cavity of the left 
l auricle is smaller in an adult subject than 
1 that ol the right ; and the ileshy fibres of the 
left auricle cross each other obliquely in stra- 
| ta differently disposed. 
Coronary arteries and veins. — Besides the 
I great common vessels, the heart has vessels 
[ peculiar to itself called the coronary arteries 
and veins, because they in some measure 
crown the basis of the heart. The coronary 
| arteries, which are two in number, go out 
from the beginning of the aorta, and after- 
I ward spread themselves round the basis of 
the heart, to the substance of which they send 
| numerous ramifications. 
Vieussens believed that some of the branch- 
-es of the coronary artery opened into the ca- 
| vities of th* ventricles and auricles ; for by 
j throwing a line injection into these arteries, 
he found it ru£ out into all sides of the right 
ventricle and auricle. Thebesius ot Aile- 
| mand being nearly of the same opinion, en- 
[ deavoured to prove that there were veins 
which carried part of the blood from the co- 
I ronary arteries immediately into the cavities 
j of the heart ; and these have therefore got 
| the name of veins of Thebesius, though lie is 
not the first discoverer. Winslow, Haller, 
and several others describe such veins ; but 
Duverney, after injecting the heart of an 
[ elephant, doubts of their existence. Senac, 
who has paid much attention ter this subject, 
denies it altogether ; and Sabatier coincides 
with him in opinion. 
There are seldom more than two arteries, 
of which one lies toward the right hand, the 
other toward the left of the anterior third 
j part of the circumference of the aorta. The 
right coronary artery runs in between the 
basis and right auricle, all the way to the flat 
[ side of the heart, and so goes halt-way round. 
The left artery has a like course between the 
basis and left auricle, and before it turns on 
the basis, it sends off a capiuil branch which 
runs in between the two ventricles. Another 
' principal branch goes off from the union of 
the two arteries on the fiat side of the heart, 
•which running to the apex, there joins the 
other branch, 
The .coronary veins are distributed exte- 
■ riorly much in the same manner. The 
largest opens into the posterior inferior part 
of the right auricle, by an orifice which is 
furnished with a valve first described by Eu- 
stachius. Besides the coronary veins, the 
■heart has other anterior veins, which have 
been called by Vieussens venie innominate. 
Some of them go into the right auricle, others 
end in the right ventricle ; and there are 
. -other veins still smaller, which are found in 
the substance of the heart, and which termi- 
nate in the right sinuses and auricle. 
Particular situation of the heart. — The heart 
VOL. I. 
ASrATUSTr; 
lies almost transversely on the diaphragm. tbA i 
greatest part of it being i» tK« no. i Wivy ol 
the thorax, and the apex being turned toward 
the bony extremity of the sixth true rib. The 
basis is toward the right cavity ; and both 
auricles, especially the right, rest on the dia- 
phragm ; but the situation of the heart during 
life changes a little, according to the state of 
respiration, and to the position of the body. 
The origin or basis of the pulmonary ar- 
tery is, in this natural situation, the highest 
part of the heart on the fore side ; and the 
trunk of this artery lies in a perpendicular 
plane, which may beperceived to pass between 
the sternum and spina dorsi. T herefore some 
part of the basis of the heart is in the right 
cavity of the thorax ; and the rest, all the way 
to the apex, is in the left cavity ; and it is for 
this reason that the mediastinum is turned to- 
ward that side. 
According to this true and natural situation 
of the heart, the parts are commonly said to 
be on the right side, or rather anterior, and 
those on the left side posterior ;■ and that side 
of the heart which is thought to be the fore 
side, is naturally the upper side, and the back 
side consequently the lower side. 
The lower side is very fiat, lying wholly on 
the diaphragm ; but the upper side is a little 
convex through its whole length, in the di- 
rection of the septum, between the ven- 
tricles. 
Uses in general. — The heart, and parts be- 
longing to it, are the principal instruments of 
the circulation of the blood. The two ven- 
tricles ought to be considered as two sy- 
ringes, so closely joined together as to make 
i) ut one body ; and furnished with suckers, 
placed in contrary directions to each other, 
so that by drawing one of them a fluid is let 
in, and forced out again by the other. 
Lungs. 
Situation and general figure. — The lungs 
are two large spongy bodies, of a reddish co- 
lour in children, greyish in adult subjects, 
and bluish in old age ; tilling the whole ca- 
vity of the thorax, one !■ ing seated in the 
right side, the other in the left, parted by the 
mediastinum and heart ; and ofa figure answer- 
ing to that of the cavity which contains them ; 
that is, convex next the ribs, concave next 
the diaphragm, and irregularly Hatted and 
depressed next the mediastinum and heart. 
Division and figure in particular. — They 
are distinguished into the right and left lung ; 
and each of these into two or three portions, 
called lobes, of which the right lung has com- 
monly three, or two and a half, and the left 
lung two. The right lung is generally larger 
than the left, answerably to the cavity of the 
breast, and to the obliquity of the mediasti- 
num . 
In the lower edge of the left lung there is 
an indented notch or sinus, opposite to the 
apex of the heart, which is therefore never 
covered by that lung, even in the strongest 
respiration ; and consequently the apex of 
the heart and pericardium may always strike 
against the ribs, the lungs not surrounding 
the heart in the manner commonly taught. 
Structure. — The substance . of the lungs is 
almost all spongy, being made of an infinite 
number of membranous cells, and of different 
sorts of vessels spread among the cells in in- 
numerable ramifications. 
M 
SC) 
i r> — i- * — : *;•- - • — , a 
membrane continued from each pieuca* 
which is commonly said to be double ; but 
what is looked upon as the inner membrane, 
is only an expansion and continuation of a 
cellular substance, which shall be spoken of 
after we have described the vessels of the 
viscus. 
Bronchia.- — The vessels which compose 
part of the substance of the lungs are of three 
or four kinds ; the principal of these are air- 
vessels and blood-vessels. The air-vessels 
make the. chief part, and are termed bron- 
chia. 
These bronchia are conical tubes, com- 
posed of an infinite number of cartilaginous 
fragments, like so many irregular arches of 
circles, connected together by a ligamentary 
elastic , membrane ; and disposed in such a 
manner, that the lower easily insinuates them- 
selves within those above them. 
They are lined on the inside by a very fine 
membrane, which continually discharges a 
mucilaginous fluid ; and in the substance of 
the membrane are a great number of small 
blood-vessels, and on its convex side many 
longitudinal lines, which appear to be partly 
lieshy, and partly made up of an elastic sub- 
stance of another kind. 
The bronchia are divided, in all directions, 
into an infinite number of ramifications, 
which diminish gradually in size ; and as they 
become capillary, change their cartilaginous 
structure into that of a membrane. Besides 
these very small extremities of this numerous 
series of ramifications, we find that all the 
subordinate trunks, from the greatest to the 
smallest, send out from all sides a vast num- 
ber of short capillary tubes of the same 
kind. 
V esiculs bronchiajes.— Each of these bron- 
chial tubes is widened at the extremity, and 
thereby formed into a membranous cell, com- 
monly called a vesicle. These cells or folli- 
culi are closely connected together in bun- 
dles ; each small branch producing a bundle 
proportionable to its extent, and the number 
of its ramifications. 
Lobuli. — These small vesicular or cellulous 
bundles are termed lobules ; and as the great 
branches are divided into small rami, so tire 
great lobules are divided into several small 
ones. The cells or' vesicles of each lobule 
have a free communication with each other, 
but the several lobules do not communicate 
so readily. 
Interlobular substance. — The lobules ap- 
pear to be distinctly parted by another cellu- 
lar substance, which surrounds each of them 
in proportion to their extent, and fills up the 
interstices between them. This substance 
forms likewise a kind of irregular membra- 
nous cells, which are thinner, looser, nnd 
broader, than the bronchial vesicles. 
This substance is dispersed through every 
part of the lungs, forms cellulous or spongy 
vaginae, which surround the ramifications of 
the bronchia and blood-vessels, and is after- 
wards spread over the outer surface of each 
lung, where it forms a kind of fine cellulsif 
coat, joined to the general covering of that 
viscus.’ 
When w-e blow into this interlobular sub- 
stance, the air compresses and flattens the 
lobuli ; and when we blow into the bronchial 
vesicles they presently swell ; and if w-e con- 
tinue to blow with force, the air passes iusen- 
