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Beginning at the cut portion of the abdominal wall, lift the thin lining of the peritoneum and carefully follow it toward the back and central portion of the abdomen. Observe whether it extends back of or in front of the kidneys, the aorta, and the inferior vena cava.
The wall of the right ventricle may now be raised and the cavity exposed. Now cut through the middle of the loosened ventricular wall from the apex to the middle of the right auricle, laying it open for observation. Observe the openings into the auricle, there being one each for the vena cava superior, the vena cava inferior, and the coronary vein.
The superior vena cava receives blood from the head and the upper extremities; the inferior vena cava, from the trunk and the lower extremities; and the coronary veins, from the heart itself. With the left auricle, the four pulmonary veins. These receive blood from the lungs and empty it into the left auricle. With the right ventricle, the pulmonary artery.
Thence sprang a person who was a second Indra in form. Clad in mail, armed with scimitars, bows, and arrows, and well-versed in the science of weapons, he was fully acquainted with the Vedas and their branches. The son of Vena then, with joined hands, said unto those great Rishis, 'I have attained an understanding that is very keen and that is observant of righteousness.
That in one sense he was right the jugular, which the other had probably opened, runs into the vena cava, and may, with some latitude, be considered a superior branch of it; therefore, thus far the first man had punctured the vena cava, which I had done many hundred times; but that the point of union of the four principal veins that form the vena cava was too securely seated in the upper part of the thorax for any lancet to reach it.
Hence in the embryo, there is almost no use for the liver, but the umbilical vein passes directly through, a foramen or an anastomosis existing from the vena portae.
The way the ancients looked at this matter was, that the food, after being received into the alimentary canal, was then taken up by the branches of this great vein, which are called the 'vena portae', just as the roots of a plant suck up nourishment from the soil in which it lives; that then it was carried to the liver, there to be what was called "concocted," which was their phrase for its conversion into substances more fitted for nutrition than previously existed in it.
Harvey, by resorting to vivisections of lower animals and reptiles, soon demonstrated beyond question the fact that the veins do carry the return blood. "But this, in particular, can be shown clearer than daylight," says Harvey. "The vena cava enters the heart at an inferior portion, while the artery passes out above.
This carries it, through its different branches, all over the body, where the tissues suck out their food and oxygen through the walls of the capillaries, and return it through the small veins into the large vein pipes, which again deliver it into the vena cava, and so to the right side of the heart from which we started to trace it.
All the cavities of the heart are lined with a smooth, delicate membrane, called the endocardium. Semilunar valves. 2. Tricuspid valve. 3. Mitral valve. 4. Right auricle. 5. Left auricle. 6. Right ventricle. 7. Left ventricle. 8. Chordæ tendineæ. 9. Inferior vena cava. 10. Superior vena cava. 11. Pulmonary artery. 12. Aorta. 13. Pulmonary veins.
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