To understand thoroughly the process of embalming as described in
the preceding chapter, it will be necessary to give here a brief
explanation of the circulatory system; also to explain the position
of the different parts of the viscera, to which reference has been
made.
The arteries commence from the great arterial trunk, called the
aorta, and their branches are distributed to all parts of the
system; they are dense in structure, and preserve for the most part
their cylindrical form when emptied of their blood, which is their
condition after death.
The aorta arises from the left ventricle, at the middle of the root
of the heart; it ascends at first forwards and to the right, then
curves backwards and to the left, and descends on the left side of
the vertebral column, to the fourth lumbar vertebra; here it is
divided into the arch and descending aorta.
It should be here remembered that most of the branches, which spring
from the great artery and vein, are double, that is, each right
branch has a corresponding one on the left side—so that there are,
for instance, the right and left carotid arteries, the right and
left jugular veins, etc. From the arch of the aorta are sent off
those arteries which are distributed to the head and arms; the
principal ones among these are named as follows:
The carotid artery, which ascends in the side of the neck and divides
into the temporal artery which is distributed in the temple, and the
facial artery which supplies the face, and also sends a branch called
the _internal carotid_ to the parts within the skull. The sub-clavian
artery, lying beneath the clavicle, or collar bone—that part of
the continuation of this artery which passes through the axilla or
arm-pit, is called the axillary artery; its continuation in the upper
part of the arm, the brachial artery; and in the fore-arm it divides
into the radial and ulnar arteries, which are distributed to the
hands and fingers.
The principal branches of the descending aorta are as follows:
The iliac artery, which on passing into the thigh becomes the
femoral artery, and, in the leg divides into the tibial and peroneal
arteries, which form numerous branches for the supply of the leg and
foot.
Before dividing into the iliac arteries the descending aorta gives
off several important branches, as the cœliac artery, from which the
stomach and liver are supplied; the renal artery, which goes to the
kidneys, and the mesenteric artery to the intestines; besides many
other sub-divisions in various parts of its course.