ANATOMY. 
In a healthy petTon, tiling fnfficient exercife of body, 
the blood moves with fuch a velocity, as fuffices to deli¬ 
ver as much of it by the vena cava to the heart, as is fent 
out by the aorta. But reft or inactivity of body, and a 
weaknefs of the contracting fibres of the heart and other 
mufcles, frequently render the motion of the venal blood 
more difficult. Hence follow the varices in women with 
child, and the piles; which latter are alfo partly owing to 
the deficiency of valves in the vena portarum. Hence alfo 
the menfes. And, when the veins return their blood too 
ftowly to the heart, the fubtile vapours ftagnate; whence 
that frequency of oedematous fwellings in weak people. 
The time in which an ounce of blood, fent out from the 
left ventricle of the heart, returns to the right, and which 
is commonly reckoned the time in which the greater cir¬ 
culation is performed, is uncertain. Suppofe the quan¬ 
tity of blood thrown out of the heart at every puliation 
to be ii ounces, and the whole quantity of the blood 
to be 336 ounces, then a complete circulation is per¬ 
formed in the time of 224 pulfutions; that is, in about 
three minutes! 
OF THE FEINS. 
The blood diftributed through the body by the aorta 
and arteria pulmonaris, returns to the heart by three kinds 
of veins, called vtna cava, vena porta:, and vena pulmonaris. 
The vena cava carries back to the right auricle of the 
heart the blood conveyed by the aorta to all parts of the 
body, except what goes by the arteriae coronariae cordis. 
It receives all this blood from the arterial ramifications in 
part direiftly, and in part indirectly. The vena portae re¬ 
ceives the blood carried to the floating vifeera of the ab¬ 
domen by the arteria caeliaca and the two mefentericae ; 
and conveys it to the vena hepatica, and from thence to 
the vena cava. The venae pulmonares convey to the pul¬ 
monary finus, or left auricle of the heart, the blood car¬ 
ried to the lungs by the arteria pulmonaris. And to thefe 
three veins two others might be added, viz. thofe which 
belong particularly to the heart, and to its auricles, and 
the finufes of the dura mater. 
The vena cava goes out from the right auricle of the 
heart by two large feparate trunks, almoft direCtly oppofite 
to each other, one running upward, called vena cavaJ'upc- 
rior ■ the other downward, called vena cava inferior. The 
vena cava fuperior is diftributed chiefly to the thorax, head, 
and upper extremities, and but very little to the parts be¬ 
low the diaphragm. The vena cava inferior is diftributed 
chiefly to the abdomen and lower extremities, and but very 
little to the parts above the diaphragm. The ancients called 
the fuperior vena cava afeendens ; and the inferior, defeendens-, 
having regard only to the great tubes, and to their divifion 
into trunks and branches. Several moderns have retained 
thefe names, but in a contrary fignification, to accommo¬ 
date them to the motion of the blood, which defeends by 
the cava fuperior, and afeends by the cava inferior. 
The fuperior vena cava runs up from the right auricle 
of the heart, almoft in a direft courfe for about two fin¬ 
gers breadth, lying within the pericardium, in the right 
fide of the trunk of the aorta, but a little more anteriorly. 
As it goes out of the pericardium, it is inclined a little to 
the left hand, and then runs up a little higher than the 
curvature of the aorta. At this place it terminates by a 
bifurcation or divifion into two large branches or fubor- 
dinate trunks, one of which runs towards the left fide, the 
other towards the right. Thefe two branches are named 
fubclavice, as lying behind, and, in fotne meafure, under 
the claviculae, both in the fame manner. They are of un¬ 
equal lengths, becaufe the trunk of the vena cava does 
not lie in the middle of the thorax, but towards the right 
fide, where the left fubclavian arifes as well as the right; 
and confequently the left is the iongeft. The trunk of 
the fuperior cava, from where it leaves the pericardium to 
the bifurcation, fends out anteriorly leveral fniall branches, 
which fometimes arife feparately, and fometimes by fmaH 
common trunks. Thefe branches are the vena mediaftina, 
pericardia, diaphragmatica fuperior, thyinica, mammaria 
627 
interna, and trachealis; the Taft of which go out fome¬ 
times behind the bifurcation. All thefe final! branches 
from the trunk of the cava fuperior are termed dextree ; 
and their fellows on the other fide, called fniflrte, do not 
arife from the trunk, becaufe of its lateral lituation, but 
from the left fubclavian. Pofteriorly, a little above the 
pericardium, the trunk of the fuperior cava fends out a 
capital branch, called vena azygos, or vena fine pari, which 
runs down on the right fide of the bodies ofthe vertebrae 
dorfi, almoft to the diaphragm; giving off the greateft 
part of the venae intercoftales and lumbares fuperiores. 
The two fubclavias run laterally or toward each fide ; and 
terminate as they go out of the thorax, between the firft 
rib and clavictila, immediately before the anterior infertion 
of the mufculus fealenus. The right fubclavian, which is 
the fhorteft of the two, commonly fends out four capital 
branches; the jugularis externa, jugularis interna, verte- 
bralis, and axillaris ; which laft is rather a continuation 
than a branch of the fubclavia. The left fubclavian gives 
off the fmall veins on the left fide, anfwering thole on the 
right fide that come from the trunk of the fuperior cava, 
viz. the mediaftina, pericardia diaphragmatica fuperior, 
thymica, mammaria interna, and trachealis. Next to thefe 
fmall veins called finijlrce, it detaches another fmall branch 
called intercofia/is fuperior finijlra ; and then four large 
branches like thole from the right fubclavian, viz. the 
jugularis externa, jugularis interna, vertebralis, and axil¬ 
laris ; which are all termed finijlrce. The external jugular 
veins are diftributed chiefly to the outer parts of the throat, 
neck, and head; and fend a fmall vein to the arm, named 
cephalica, which affifts in forming a large one of the fame 
name. The internal jugular veins go to the internal parts 
of the neck and head, communicating with the finufes of 
the dura mater, and in feveral places with the external 
jugular veins. The vertebral veins pafs through the holes 
in the tranfverfe apophyfes of the vertebrae of the neck, 
fending branches to the neck and occiput. They form the 
finus venales of thefe vertebrae, and communicate with the 
finufes of the dura mater. The'axillary veins are conti¬ 
nuations of the fubclavice, from where thefe leave the tho¬ 
rax to the axillae. They produce the mammariae internae, 
thoracicae, fcapulares or humerales, and a branch to each 
arm; which, together with that from the external jugu¬ 
laris, forms the vena cephalica. Afterwards the axillary 
vein terminates in the principal vein of the arm, called 
bafilica ; which, together with the cephalica, is diftributed 
by numerous ramifications to all parts of the arm, fore* 
arm, and hand. 
The portion of the inferior vena cava, contained in the 
pericardium, is very fmall, being fcarcely the twelfth 
part of an inch on the fore-part, and not above a quarter 
of an inch on the back-part. From thence it immediately 
perforates the diaphragm, to which it gives the venae dia- 
phragmaticae inferiores or phrenicae. It pafles next be¬ 
hind the liver, through the great finus of that vifens, to 
which it furnifltes feveral branches, termed vena: hepatkat. 
In this courfe it inclines a little towards the fpina dorfi and 
aorta inferior; the trunk and ramifications of which it af¬ 
terwards accompanies in the abdomen, all the way to the 
os facrum ; the arteria caeliaca and the two mefentericae 
only excepted. Thus the inferior cava lends out on each 
fide, in the fame manner with the aorta, the vente adipofae, 
renales, fpermaticre, lumbares, and facrae. Having reached 
to the os facrum, it lofes the name of cava; and, termi¬ 
nating by a bifurcation, like thit of the defeending aorta, 
it forms the two venae iliacte. Thefe iliac veins having 
given off the hypogaftricas, with all their ramifications, to 
the vifeera of the pelvis, and to fome other external and 
internal neighbouring parts, go out of the abdomen, under 
the ligamentnm Failopii, and there take the name of vents 
crurates. Each crural vein fends off numerous ramifica¬ 
tions to all the lower extremity ; befides the vena faphena, 
which goes out near the,origin of the cruralis, and, running 
along this whole extremity, detaches many ramifications 
ali the way to the foot, 
Thus 
