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In some men of sturdier frame and stouter make the right auricle is so strong, and so curiously constructed on its inner surface of bands and variously interlacing fibres, that it seems to equal in strength the ventricle of the heart in other subjects; and I must say that I am astonished to find such diversity in this particular in different individuals.
From the right ventricle a large vessel called the pulmonary artery passes to the lungs, and from the left ventricle a large vessel called the aorta arches out to the general circulation of the body. The openings from the ventricles into these vessels are guarded by the semilunar valves. Each valve has three folds, each half-moon-shaped, hence the name semilunar.
These little irregular stimuli proceeding from the auricle reach the auriculoventricular node and are transmitted to the ventricle as rapidly as the ventricle is able to react. Such rapid stimuli may soon cause death; or, if for any reason, medicinal or otherwise, the ventricle becomes indifferent to these stimuli, it may not take note of more than a certain portion of the stimuli.
The two largest veins in the body, the superior vena cava and the inferior vena cava, open into the right auricle. These two veins bring venous blood from all parts of the body, and pour it into the right auricle, whence it passes into the right ventricle.
The bottle of the gall subtracts from thence all the superfluous choler; whence it is brought to another shop or work-house to be yet better purified and fined, that is, the heart, which by its agitation of diastolic and systolic motions so neatly subtilizeth and inflames it, that in the right side ventricle it is brought to perfection, and through the veins is sent to all the members.
If the left ventricle is unable to receive and therefore send out into the systemic circulation sufficient blood to dilate the peripheral capillaries under the irritation of the baths or the vasodilator effects of the baths, the bath treatment does harm instead of good.
When this auricle becomes filled, it contracts and forces the stream of blood through an opening in the right ventricle of the heart, which in turn sends it on to the lungs, where it is distributed by millions of hair-like blood vessels to the air cells of the lungs, of which we have spoken. Now, let us take up the story of the lungs at this point.
The muscular substance of the heart itself is supplied with nourishment by two little arteries called the coronary arteries, which start from the aorta just above two of the semilunar valves. The longest route a portion of blood may take from the moment it leaves the left ventricle to the moment it returns to it, is through the portal circulation.
At times the edges of the valves may grow together from ulcerative inflammation, and the lumen thus be diminished in size; or projecting vegetations may interfere with the opening of the valve and with the flow of blood. With such narrowing the left ventricle more or less rapidly hypertrophies to overcome its increased work.
Man has been defined as the only animal possessed of two hands terminating his fore limbs, and of two feet ending his hind limbs, while it has been said that all the apes possess four hands; and he has been affirmed to differ fundamentally from all the apes in the characters of his brain, which alone, it has been strangely asserted and re-asserted, exhibits the structures known to anatomists as the posterior lobe, the posterior cornu of the lateral ventricle, and the hippocampus minor.
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