Volume 1

The physiology of man : designed to represent the existing state of physiological science as applied to the functions of the human body / by Austin Flint.

  • Flint, Austin, 1836-1915.
Date:
1866-1874
Catalogue details

Licence: Public Domain Mark

Credit: The physiology of man : designed to represent the existing state of physiological science as applied to the functions of the human body / by Austin Flint. Source: Wellcome Collection.

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    grave results. It has already been noted that on the right side the Inngs are protected by an insufficiency of the auri- culo-ventricular valves, which does not exist on the left side, allowing of a certain degree of regurgitation when the heart is acting with unusual force, and thus relieving, to a certain extent, the pulmonary system. This was pointed out by Mr. King of London, and called the safety-valve function of the right ventricle.' We have noticed, in the heart of the ox, a like disparity between the aortic and pulmonic semilunar valves. If these be exposed on both sides by cutting away portions of the ventricles, and a current of liquid be forced against them through the vessels, the aortic valves will be found to entire- ly prevent the passage of the liquid, even under very great pressu.re, while the pulmonic valves permit regurgitation un- der a very inconsiderable pressure. A little reflection will make it evident that when the heart is acting with undue force it is quite as important to relieve the lungs by a certain amount of regurgitation from the pulmonary artery, as by insufficiency of the tricuspid valves. This insufficiency is important, both at the auriculo-ventricular and pulmonic ori- fices, in protecting the delicate structure of the lungs from the variations in force to which the action of both ventricles is constantly liable. On microscopic examination of the circulation in the lower animals, as the frog, the movement of blood in the ca- pillaries of the lungs does not present any differences from the capillary circulation in other parts; except that the vessels seem more crowded with corpuscles, and there is no still layer next their walls. There are no forces of any moment which are superadded to the action of the right ventricle, in the production of the arterial, capillary, or venous circulation in the lungs; but there are certain conditions which may obstruct the flow of blood through these parts. We have already noted the effect of introduction of air into the veins, in blocking up the capil- 4 Guy's Hospital Reports, IBS'?.