A Treatise on the Diseases of the Ear

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1901. Excerpt: ... questions to be considered. In the first place, it is necessary to determine the extent to which its vibrations are transmitted to the walls of the auditory meatus and the tympanum; and in the second place, the degree in which the auricle reflects the soundwaves which reach its surface, towards the column of air in the external meatus. In former times this reflection was regarded as the sole, or, at all events, the principal function of the auricle; but at the present day, conduction of sound is considered to be its most important office. Owing to its firmness and elasticity, the expanded auricle is well adapted for the reception and transmission of sound-waves, some of which at the same time it reflects. Irrespective of its elevations and depressions, it forms a somewhat flattened plate, impulses against the surface of which are transmitted over it in every direction. These impulses are most freely conducted when the sonorous waves impinge perpendicularly upon the auricle, and the nearer this direction is approached the more extensive will the vibrations become. But the auricle is not a level surface, and the whole of it can never be acted upon in a perpendicular direction by sonorous undulations proceeding from a given point. The importance of the complicated elevations and depressions on its surface thus becomes manifest; for undulations impinging upon the auricle from any direction must fall advantageously, i.e., perpendicularly or nearly so, upon some of them, and then be propagated without much loss of force. The most favourable position for the transmission of sound is when the ear is so situated that the plane of the largest portion of its surface is directed perpendicularly towards the source of the stimulus. It is very difficult to estimate the ...