. Diseases of the ear : a text-book for practitioners and students of medicine. is inserted into his own auditory canal, is able to recognizethe moment when the air enters the tympanum, by its impactupon this delicate partition. The sound produced under nor-mal conditions when the tympanum is suddenly inflated wemay denominate, for convenience, the sound of impact. Itis of sharp, metallic character, and is due to the stretchinggf the membrana tympani by the sudden condensaUon ofthe air within the middle ear. This sound seems to originatein the ear of the observer on account of the extreme thin
. Diseases of the ear : a text-book for practitioners and students of medicine. is inserted into his own auditory canal, is able to recognizethe moment when the air enters the tympanum, by its impactupon this delicate partition. The sound produced under nor-mal conditions when the tympanum is suddenly inflated wemay denominate, for convenience, the sound of impact. Itis of sharp, metallic character, and is due to the stretchinggf the membrana tympani by the sudden condensaUon ofthe air within the middle ear. This sound seems to originatein the ear of the observer on account of the extreme thinnessof the interposed partition, and the direct conveyance of thesound waves to his ear. Under normal conditions but asingle sharp metallic click or snap is heard. This may befollowed later by a similar sound of lower pitch and of lessintensity, due to the return of the membrana to a conditionof equilibrium in virtue of its elasticity. A familiarity withthese signs in health enables the observer to interpret cor-rectly the significance of any modification in their character. Fig. 43.—Auscultation tube. due to pathological conditions. It is sometimes stated thatauscultation is a procedure of little diagnostic value, but I canonly say that the otologist who would take this ground, mightbe compared with a physician who would consider himselfable to judge of intrathoracic conditions without availinghimself of auscultation of the chest. Auscultation certainlyaffords us a valuable means of recognizing certain conditionswithin the tympanum and Eustachian tube, if practiced suffi-ciently long to enable one to interpret the significance of thevarious sounds heard. Methods of Inflation.—The earliest method of inflation ofthe middle ear is that which bears the name of its discoverer,Valsalva. It is executed by the patient compressing the alasnasi between the thumb and finger of one hand, thus closingthe nostrils; at the same time the mouth is closed and the at- 104 PHYSICAL EXAMINATIO
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