Misconceptions regarding arterial elasticity / by G. A. Gibson.

Date:
1896
Catalogue details

Licence: Public Domain Mark

Credit: Misconceptions regarding arterial elasticity / by G. A. Gibson. 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.

    9/16 (page 7)
    his researches upon the thermo-elastic properties of animal tissues he found that these differ entirely from those of most inorganic substances. When a metal is compressed it becomes warmer, and when it is stretched it become colder; every animal tissue gives opposite results. His experiments were performed with the thermopile and galvanometer, and he found that the temperature of all animal tissues rises on stretching and falls again when they are relaxed. The pro- duction of restitution pressure is therefore accompanied by the generation of heat. The variation of temperature increased directly with the weights employed. Conversely, he has also proved that when heat is applied animal sub- stances contract and that when they are allowed to cool they again expand. Animal tissues, therefore, are like bismuth, exceptions to the general rule that heat causes expansion and cold contraction, and they therefore resemble caoutchouc. These results have not such direct bearing upon the matter to be more especially discussed, but inasmuch as they are of vital importance in observing certain differ- ences between the elastic properties of animal tissues and inorg^anic substances they cannot well be passed over. As regards the relation between internal pressure and the cubic capacity of the arteries Professor Roy investigated the degree in which a portion of artery expands with each successive increase in the internal pressure. The method employed was to enclose a portion of artery, so arranged that it could be distended by any internal pressure, in a small vessel containing olive oil, the variation of whose contents were recorded. The intra-arterial pressure was raised by increments of 10 mmHg until a pressure of from 100 to 200 inmHg was attained. The increments of capacity increase in proportion to the increments of arterial pressure until a certain point is reached, after which they diminish, and the most interesting result is that the arterial walls are most distensible at pressures corresponding more or less ex^tly to their normal blood pressure. Investigations upon veins show a very different relation between internal pressure and cubic capacity, inasmuch as the maximum dis- tensibility occurs with pressures immediately above zero. Zwaardemaker'’^ found that with regard to the arteries the results of Professor Roy’s researches were in close accord with the conclusions to which he was led by a series of investigations made by himself. Geneeskunde;