. Annual report of the Board of Regents of the Smithsonian Institution. Smithsonian Institution; Smithsonian Institution. Archives; Discoveries in science. THE SENSE OF HEARING. 163 means always thoroughly open, but usually its walls lie close to one another, although so loosely that every inward curvature of the tympanum readily separates them for the expulsion of a portion of the air within the cavity. It opens not so readily to the air of the pharynx; a peculiar effort is necessary to effect an entrance of the air in the above mentioned experiment. In ordinary speaking and singing this effo
. Annual report of the Board of Regents of the Smithsonian Institution. Smithsonian Institution; Smithsonian Institution. Archives; Discoveries in science. THE SENSE OF HEARING. 163 means always thoroughly open, but usually its walls lie close to one another, although so loosely that every inward curvature of the tympanum readily separates them for the expulsion of a portion of the air within the cavity. It opens not so readily to the air of the pharynx; a peculiar effort is necessary to effect an entrance of the air in the above mentioned experiment. In ordinary speaking and singing this effort is never used; the air coming from the lungs chooses the broad and unobstructed outlet of the mouth or nostril, and passes by the orifice of both ear-tubes without opening them; consequently, no sound- producing air-waves come ordinarily by this channel to the organs of hearing. That happens only when, in speaking or singing, we make a peculiar effort, and then indeed we suddenly hear our voice, which before sounded as coming from without, with deafening force and as if it originated in tlie ear itself. This last circumstance is of particular significance; we shall see further on that, in idea, we then only judge the source, which we regard as cause of a sound, to he with- out us, when the waves thereby generated reach our organ of hearing through the external meatus of the car; but whenever it happens that this is impervious to the air-waves, we seek the source of the sound icithin ourselves, even when it is really without. There can, therefore, be no question of hearing our own voice through the Eustachian tube, not to say of its destination for this purpose. We could submit more of such hypotheses to criticism were it worth while. Much has been idly said respecting a strengthening of the waves of sound in the cavity of the tympanum through resonance, but a closer examination of these suppositions would require a special investigation of the physical nature of re- sonance,
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