Volume 1
A text-book of experimental psychology : with laboratory exercises / by Charles S. Myers.
- Charles Samuel Myers
- Date:
- 1911
Licence: Public Domain Mark
Credit: A text-book of experimental psychology : with laboratory exercises / by Charles S. Myers. Source: Wellcome Collection.
44/370 page 24
![has the advantage of possessing only feeble powers of reson¬ ance. Were the tympanic membrane flatter denser, and freer, it would resonate more powerfully to one particular tone than to others,—a feature obviously harmful to good hearing. Its peculiar form and connexions allow it to respond fairly equally to the wide range of tones to which the ear is sensible (exp. 19). The most recent researches on the function of the tensor tympani muscle have been conducted by placing a minute mirror on the tympanic membrane of a living person and photographing the movements of the membrane by means of a beam of reflected light. The results show that an auditory stimulus, so long as it lasts, causes a prolonged contraction of the tensor tympani muscle. Thereby the amplitude of the vibratory excursions of the membrane which it executes in response to the stimulus is reduced, the membrane being protected from excessive vibration and thus from risk of damage. It had previously been supposed that the tensor tympani muscle contracts with different force according to the pitch of the stimulus, tuning the membrane so that it responds with maximal sensitiveness to tones of different pitch. But the experiments that have been advanced in favour of this accommodatory function of the muscle are not convincing. They were performed on dead animals, the tension of the membrane being varied by applying different degrees of artificial traction to the tendon of the muscle. The position of the stapes is controlled by the stapedius muscle, which contracts during attentive listening. Its action is to pull the ossicles towards the tympanic membrane, lessen¬ ing the curvature of the latter. Consequently the pressure within the inner and middle ear falls, the tympanic membrane vibrates more freely, and the keenness of hearing is increased. On the other hand, the pressure within the middle ear is raised during yawning (owing to the accompanying con¬ traction of the tensor tympani), or when air is forced through the Eustachian tube into the tympanic cavity: in either case a marked damping of loud and deep tones results.] [The Relations of Noise to Tone.—In order that pendular](https://iiif.wellcomecollection.org/image/b3135984x_0001_0044.jp2/full/800%2C/0/default.jpg)
