Sound / by John Tyndall.

  • Tyndall, John, 1820-1893.
Date:
1875
Catalogue details

Licence: Public Domain Mark

Credit: Sound / by John Tyndall. Source: Wellcome Collection.

    110/464 (page 72)
    Eustachian tube remains closed, the membrane will be pressed outwards. Pain is felt in both cases, and partial deafness is experienced. I once crossed the Stelvio Pass by night in company with a friend who complained of acute pain in the ears. On swallowing his saliva the pain in- stantly disappeared. By the act of swallowing the Eusta- chian tube is opened, and thus equilibrium is established between the external and internal pressure. It is possible to quench the sense of hearing of low sounds by stopping the nose and mouth, and trying to ex- pand the chest, as in the act of inspiration. This effort partially exhausts the space behind the tympanic mem- brane, which is then thrown into a state of tension by the pressure of the outward air. A similar deafness to low sounds is produced when the nose and mouth are stopped, and a strong effort is made to expire. In this case air is forced through the Eustachian tube into the drum of the ear, the tympanic membrane being distended by the pres- sure of the internal air. The experiment may be made in a railway carriage, when the low rumble will vanish or be greatly enfeebled, while the sharper sounds are heard with undiminished intensity. Dr. Wollaston was expert in closing the Eustachian tube, and leaving the space behind the tympanic membrane occupied by either compressed or rarefied air. He was thus able to cause his deafness to continue for any required time without effort on his part, always, however, abolishing it by the act of swallowing. A sudden concussion may produce deafness by forcing air either into or out of the drum of the ear, and this may account for a fact noticed by myself in one of my Alpine rambles. In the summer of 1858, jumping from a clitf on to what was supposed to be a deep snow-drift, I came into rude collision with a rock which the snow barely covered. The sound of the wind, the rush of the glacier-torrents, and all the other noises which a sunny day