The forces which carry on the circulation of the blood / by Andrew Buchanan.
- Andrew Buchanan
- Date:
- 1874
Licence: Public Domain Mark
Credit: The forces which carry on the circulation of the blood / by Andrew Buchanan. Source: Wellcome Collection.
Provider: This material has been provided by the Francis A. Countway Library of Medicine, through the Medical Heritage Library. The original may be consulted at the Francis A. Countway Library of Medicine, Harvard Medical School.
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![the chest extends over the whole vascular system; for at the moment of inspiration the weight of the atmosphere bears down the column of blood simultaneously at the very beginning of the arteries and at the very end of the veins, thus rendering it quite certain that the same pressure takes place also at every intermediate point. As the veins become smaller the oscillations become less extensive, just like the visible changes in the diameter of the veins. This diminution of the range of the oscillations as we recede from the heart, whether in the veins or in the arteries, has never been interpreted in its full significance; and will, hereafter, be looked to with great interest, seeing that correct theory shows the range of the oscillations in the blood-vessels at any point to be inversely as the sectional area of the blood- vessels at that point, and of course directly as the velocity of the blood in the vessel subjected to experiment. Entrance of air into veins.—The depression of the arterial column produced by inspiration is small in relation to its total height; but the venous column near the heart is only one tenth as high as the arterial, and the depression of it from inspiration is relatively very great. It may be diminished to one half, or a quarter, or still less, and may even disappear altogether, and then the external air forcing its way into the vein would be carried with the current of blood onward to the heart, just as has been known to take place in operations in the vicinity of the cavity of the thorax in which large veins have been laid open. Great feebleness of the heart on the one hand, and, on the other, sighing or other very deep inspirations, are the causes which conspire to occasion the entrance of air into the veins; as must be obvious from considering that the former makes the hsemastatic column low, and the latter make the fall of the column great. Asphyxia, or cessation of breathing. — Whenever the act of breathing] ceases, from whatever cause, whether from sub- mersion in water, from tying the windpipe, from obstructing the aperture of the mouth and nostrils as in suffocation or smothering, or from compressing the windpipe as in hanging or garotting—if there be a complete arrestment of the respi-](https://iiif.wellcomecollection.org/image/b21044193_0084.jp2/full/800%2C/0/default.jpg)
