A popular essay on the laws of acoustics, and on the anatomy and physiology of the ear : followed by seventyseven cases of persons cured of deafness, being simple abstracts of each individual case / by Joseph Togno.

  • Togno, Joseph.
Date:
1834
Catalogue details

Licence: Public Domain Mark

Credit: A popular essay on the laws of acoustics, and on the anatomy and physiology of the ear : followed by seventyseven cases of persons cured of deafness, being simple abstracts of each individual case / by Joseph Togno. Source: Wellcome Collection.

Provider: This material has been provided by the National Library of Medicine (U.S.), through the Medical Heritage Library. The original may be consulted at the National Library of Medicine (U.S.)

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    SENSE OF HEARING. Hearing is the sense destined to make us acquainted with sounds. Its study, like that of the sense of sight, is divided into three parts: namely, 1st, The physical history of sound, or the exterior excitor or agent which produces the impression; on this is based the science of acoustic, which in reality is a part of the science of the motion of bodies. 2nd, The anatomical structure of the organ; and 3d, The mechan- ism of hearing. FIRST SOUND. When a body is percussed or struck, there occurs in the molecules or particles composing it, vibratory motions which gradually diminish as they extend from one body to another, like the concentric waves produced by throwing a stone into a collection of water, and at last stop. These oscillations are immediately experienced by the surrounding air in contact with the body, and are propagated from stratum to stra- tum of the atmosphere, to a certain distance; this quivering or vibra- tion is at last communicated to the ear, and there produces, first an im- pression, and then a sensation, as we shall see hereafter, which we call sound or noise. In the sense of hearing, the exterior excitant is not then the sonorous body itself, as in the case of touch; it is not even one of its integral molecules, as in the sense of taste and smell; but it is the air repeating merely the vibratory movements which the sonorous body experiences. There is no doubt that this is the manner in which sound is produced and propagated; for we may demonstrate the molecular)' oscillations both to sight and touch, either by striking a bell, or causing a string to vibrate. These sonorous oscillations are confined to the molecules of the body—for often a whole body may be put in motion, without, on that account, any sound being produced ; as, for instance, by letting go, to their natural elasticity, the branches of a pair of forceps, having pre- viously approached them near each other. In every sonorous body, we must especially consider its elasticity as its moving power. A sonorous body may be elastic by tension: such bodies, when they have only a liniary direction, are called cords, as we see in all stringed instruments ; but when they are spread out into membranes, they are then called a drum, or a tympanum; the ear of ani- mals is of this category. A sonorous body may be also elastic from the pressure of the air ; such are all wind instruments in which the air is re- tained a longer or a shorter space of time, according as it lets out the air at one or the other keyhole. Lastly, a body may be sonorous through its hardness. (The bones in which the ear is lodged are the hardest in the body.) They may be of different discription ; they may be liniary, like