On the dependence of animal motion on the law of gravity / by Henry Wiglesworth.

Date:
1849
Catalogue details

Licence: Public Domain Mark

Credit: On the dependence of animal motion on the law of gravity / by Henry Wiglesworth. 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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    internal cavityj as it must be pretty equably maintained at the temperature of the body, 98 or 100, consequently its pressure will always be the same. Nor does it appear likely that an orifice, as a kind of safety-valve, is required to vary the amount of air within, according to the variation of external pressure, allowing some to escape, when the pressure is in- creased, and to enter, when the pressure is diminished, so as to maintain the same relative tension of the membrane; for the membrana tympani itself will regulate this, even in a closed cavity. If the air be cold and heavy, and disposed to press the tympanic membrane, it will from its low vitality, and almost complete isolation, likewise share in the tem- perature contract, and prevent any encroachment upon the cavity, or increase of tension from without, while, if the air be warmer and lighter, and its pressure upon the membrane diminished, the latter will 'again shareln the change of tem- perature, relax, and give a greater surface to such pressure, thus preventing any enlargement of the cavity,* or increase of the tension from within; while, if the temperature of the contained air is shghtly affected by the temperature of the membrane itself, the consequent alteration in the pressure will be precisely what is required to maintam the balance of tension, viz., diminution of resistance (from contraction) when the pressure is increased, and increase of resistance (from expansion) when the pressure is diminished. * I may remind tlie reader, that the surface of the tympauio mem- brane is not a plane. It is concave without, and convex Avithin; doubt- less depending upon the difference in the amount of pressure, occasioned by the difference iu the temperature.