On the law which regulates the relative magnitude of the areas of the four orifices of the heart / by Herbert Davies.

  • Davies, Herbert, 1818-1885.
Date:
1870
Catalogue details

Licence: Public Domain Mark

Credit: On the law which regulates the relative magnitude of the areas of the four orifices of the heart / by Herbert Davies. 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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    discovered which determines the relative magnitude of the areas of the tricuspid, pulmonic, mitral, and aortic orifices—the four principal openings in the heart. Although to ordinary observation these orifices appear to exhibit no mutual relationship of size, there can be no doubt that an instrument so accurate in the adaptation of its valvular apparatus, and so exact in the working of its difiFerent parts, must reveal on close examination the exist- ence of laws which not only determine the force required to be impressed upon the blood traversing its chambers, but also the relative sizes of these apertures to one another. The facts and inferences which I shall adduce on this subject will tend, I believe, to throw some light upon the mechanism of the heart in its healthy state, and will explain also some points of practical interest in the pathology of that organ. , To M. Bizot in France, and Drs. Peacock and Reid in this country, are we mainly indebted for the most careful and trustworthy measurements of the circumferences of the orifices. Their measurements have been re- corded to the minuteness of the thousandth part of an inch, and yet it will, I believe, be readily admitted that the results in the form given by these distinguished observers help us but little in obtaining any definite idea of the mutual relationship of the areas of the orifices, and are destitute of any practical value in our study of the mechanism of the heart itself. Had the observations been pushed further, or, rather, had the figures been worked out into some distinct and definite shape, these observers could not have failed to discover an interesting and important law pre- siding over the areas of these orifices, and they would thus have been enabled to utilize a multitude of measurements w'hich had been obtained by considerable labour and patient research. Taking the measurements given by Dr. Peacock in the Croonian Lec- tures for 1865, we find the mean circumferences of the four orifices, ex- pressed in English inches, to be as follows:— Males. Females. Tricuspid 4’/4 4’562 Pulmonic 3*552 3*493 Mitral 4 3*996 Aortic 3*14 3*019 I will now place these valuable facts into another shape by calculating from these measurements of circumference, the areas of the respective openings. The circumference of a circular opening being known, its radius is de- termined from the formula circumference = 27rr, where tt=3*1415 ; and the radius being thus determined, the area of the opening is calculated from the formula area = 7rr^