The elastic properties of the arterial wall / by Charles S. Roy.

  • Roy Charles S. (Charles Smart)
Date:
1880
Catalogue details

Licence: Public Domain Mark

Credit: The elastic properties of the arterial wall / by Charles S. Roy. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

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    fills the vessel, i. The upper half of this vessel, the tube, k, and the por- tion of artery contain air. The piece of artery is inclosed in oil in the same kind of vessel as that described above. With this arrangement the difference in level of the mercury in the reservoir, h, and the pressure vessel, i, corresponds with the pressure within the piece of artery. By the arrangement of the silk cords the reservoir is raised or lowered in proportion to the movement of the drum of the clockwork. Since the two pulleys, c, are of equal diameter, the rate of movement, up or down, of the mercury reservoir, is exactly the same as the rate at which the blackened surface of the drum moves past a fixed point. For example, one inch of an abscissa, drawn horizontally on the drum’s surface, corresponds to a rise or descent of the mercury reservoir of exactly one inch. • In taking tracings with this arrangement the mercury reservoir is either slowly raised or slowly lowered, and, in the curves obtained, the pressures in the portion of artery are the abscissae; and, since the vertical movements of the point of the recording lever are proportionate to the variations in the capacity of the portion of artery, the ordinates of the curve obtained are the cubic capacities of specimen of artery examined. B^ the use of very wide vessels for the mercury reservoir and the pressure vessel, i, we avoid, more or less completely, the error which would otherwise be introduced owing to compression of the air contained in the upper part of the vessel, i, and in the narrow tube going from it to the cannula, as well as from the variations in capacity of the portion of artery examined. By the use of wide shallow vessels, and by taking care that as little air as possible is contained in the upper part of the compression vessel, the error due to the want of exact correspondence between the movements of the reservoir and the difference in height of the two mercury surfaces may be so greatly reduced that its influence may, in practice, be safely ignored. At first, indeed, I made corrections of my curves with the view of eliminating this error, but I soon found it to be excessively slight, and not of a kind which could possibly modify to any noteworthy extent the character of the tracings obtained. In working with this method the rate of movement of the drum was usually very slow,' so that 20 minutes, or half an hour in some cases, was passed in raising or lowering the intra-arterial pressure gradually from zero to 200 mm. of mercury, or vice versa. This AVas done with the