THE ARTERIAL SYSTEM.
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.