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The patient died one month after of another cause, and at the postmortem examination the aorta was shown to have been opened; the wound in its walls was covered with a spheric, indurated coagulum. No attempt at union had been made. Zillner observed a penetrating wound of the aorta after which the patient lived sixteen days, finally dying of pericarditis.
This impure blood passes to the capillaries of the air-cells in the lungs, where it gives off carbonic acid, and, taking oxygen from the air, then returns to the left side of the heart, from whence it is sent out through the aorta and its myriad branching arteries to every part of the body.
All the blood flows continuously through both circulations and passes the various parts in the following order: right auricle, tricuspid valve, right ventricle, right semilunar valve, pulmonary artery and its branches, capillaries of the lungs, pulmonary veins, left auricle, mitral valve, left ventricle, left semilunar valve, aorta and its branches, systemic capillaries, the smaller veins, superior and inferior venæ cavæ, and then again into the right auricle.
Touch it and feel how solid it is, and how few dangers there can be for anything placed behind it. Well, that is the rampart which has been given to the Aorta. As this descends, it slips behind the heart and takes up its place in front of the vertebral column which it follows all the way down the back, just to the top of the loins.
The second sound is, without doubt, caused by the sudden closure of the semilunar valves of the pulmonary artery and the aorta, at the moment when the contraction of the ventricles is completed. Muscular Fibers of the Ventricles.
You see, the presence of the blade in the aorta has already reduced the blood-carrying capacity of that vessel; a clot, therefore, need not be very large to stop up the aorta, and, of course, if that should occur death would ensue.
Another union is that by the pulmonary artery, and is effected when that vessel divides into two branches after its escape from the right ventricle of the heart. It is as if to the two trunks already mentioned a third were superadded, a kind of arterial canal, carried obliquely from the pulmonary artery, to perforate and terminate in the great artery or aorta.
The diagnosis has to be made from solid or cystic tumours overlying the artery; from a "pulsating aorta"; and from spinal caries; much help is obtained by the use of the X-rays. The condition usually proves fatal, either by the aneurysm bursting into the peritoneal cavity, or by slow leakage into the retro-peritoneal tissue.
But it must not be forgotten that man has a twofold respiration, one of the spirit and another of the body; and that the respiration of the spirit depends on the fibers from the brains, and the respiration of the body on the blood-vessels from the heart, and from the vena cava and aorta.
As each time the heart beats, it throws out half a teacupful of blood into the aorta, this jet sends a wave of swelling down the arteries all over the body, which can be felt clearly as far away as the small arteries of the wrist and the ankle.
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