Lectures on the heart : delivered at the Melbourne University, Victoria, during the session of 1864 / by George B. Halford.

  • Halford, George Britton, 1824-1910.
Date:
1864
Catalogue details

Licence: Public Domain Mark

Credit: Lectures on the heart : delivered at the Melbourne University, Victoria, during the session of 1864 / by George B. Halford. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    From this I hope you will see that the auriculo-ventricular valve must be closed previously to the systole of the ventricle, as in figs. 1, 2, 3, otherwise the ventricle could not thoroughly be filled, nor could the valve itself perform its office properly ; for as the ventricle contracts and its base descends, the valve would be made to yield towards the auricle at the very time it is required to be unyielding. But with the valve closed by the end of the auricular contraction, as in fig. 3, there is not only no chance of yielding towards the auricle, but the ventricle is in that condition to exert its power most instantaneously and effectively, as the prime mover—the fons et origo —of the circulation. The rapidity and power of its action ivould he impaired were any of its force expended in a backward direction, had it indeed to close the auriculo-ventricular, previously to opening the semilunar valves. But it may be asked, How can the force of the auricular contrac- tion be brought to bear upon the under or ventricular surface of the valve 1 The following preparations point to the means by which this process is effected, you observe— 1st. That if we open a ventricle and cut away the flaps of the auri- culo-ventricular valve from theirattachments, both to the zonatendinea and to the chord® tendine®, on placing the preparation in fluid, the chord® tendinese rise up like stems of aquatic plants from the musculi papillares, and from the side of the ventricle. 2nd. That when the chord® tendine® are cut off close to the under surface of the flaps of the valve, the latter are still supported at a certain level in the fluid, and their delicate margins curl upwards towards the auricle. This latter fact is more evident in the right than in the left ventricle, and was first remarked by Dr. Markham. Again, when a whole valve with the upper part]of the ventricle is cut out so as to form a muscular ring with the flaps of the valve hanging loosely, and is placed in fluid with the auricular surface upward, their delicate margins turn up as little scrolls ; when the same preparation is placed in fluid with the auricular surface downward, their edges now turn downward, which is not the case with any other part of the valve. Now, if to the above we add that the ventricle in filling is an enlarging cavity, and that this enlargement takes ptace below the attachment of the valve to the zona tendinea, and that in the elongation and upward movement of the base the valve participates; and if we remember that, even to the last drop of blood from the auricle, there is a force causing the particles of blood within the ventricle to press upon the under surface of the valve even after the auricular contraction has ceased (for it cannot be supposed that ever, even for an instant, the blood is at rest), then are we led to the following conclusions, viz. :— The chord® tendine® by position serve to open out and prop up tas stems of water-plants do their leaves) the flaps of these valves • hrm connection at the circumference with the zona tendinea
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