Cases will frequently be met where these tests give uncertain or contradic tory results. Patients will give their preconceptions instead of observing the actual perceptions, unwilling to say that they hear by bone louder in the ear which they know to be worse or confusing pal pable vibrations with their weakened au ditory perceptions. A deaf-mute will often claim to hear the fork as well rest ing on the patella as when on the mas tcid. Yet a little patience and variation of the tests will generally clear up con tradictions. The high tones are later and in less degree lost in tympanic affec tions, unless thickening of the drum head shut out some such sound tone as the impure of the watch-tick.
The catarrhally deaf usually hear rela tively or even actually better in a noise, — "paracusis Willisii"; whereas those with nerve-deafness are made worse by it. Very high tones, such as given by the Koenig rods or the Galton whistle, may be inaudible to a diseased labyrinth or portions of the gamut may be lost, while all voice-tones, as well as much deeper notes, are normally heard. These limitations must be learned and borne in mind; then the tuning-fork tests will generally be found to lead to correct diagnosis; and the many instances of mixed affection will be noted as well as those which are totally differentiated.
In affections of the Eustachian tube and in those of the external aural ductus, the sound of a vibrating diapason is al ways heard on the shut or impaired side stronger than on the crossed side. In cases of disease of the tympanic cavity without involvement of the acoustic nerve it is always heard from the direct side, though one side is more impaired than the other. In cases of diseases of the tympanic cavity with hypergesthesia of the acoustic nerve, or in cases of this condition only, the sound is head from the hypernsthetic side, but stronger on the crossed side. In cases of disease of the internal ear (atony or atrophy of the acoustic nerve), with or without impair ment of the tympanic cavity, the percep tion of the crossed sound is abolished, while sometimes the direct sound con tinues (although very weak). Masini (Bollettino delle Malattie della Gola e del Nas:o, July, 'SS).
Ability to hear the voice at a distance proportionately greater than the distance at which the sounds of a clock can be heard is a symptom of disease of the cochlea or of the acoustic nerve. Four
principal types of eases may show a dis proportionate relationship in the ability to hear these two classes of sound: 1. Aphouic voice and clock with strong tick heard at about the same distance: a rare type appearing in slight affections of the sound-conducting apparatus. 2. The voice heard about three times farther than the clock: a more frequent type, found in nerve affections of the sound conducting apparatus. 3. The voice heard at a still greater distance: fifty times farther than the clock, as in disease of the inner ear in young subjects. 4. The clock heard farther, sometimes ten times farther, than the yoke: a rare type seen only in hysterical conditions and quite characteristic of this affection. Gra denigo (Annual, 'K.
Diagnosticated in the manner outlined above there will be a small, but impor tant, group in which there has been a small-cell infiltration of the labyrinth as the result of syphilis, acquired or in herited; of cerebrospinal meningitis, or typhoid, or other fevers. The onset of the deafness may be sudden, usually without vertigo, or it may be stealthy and gradual. Acoustic hyper- sthesia may precede it, and the condition may be very unequal on the two sides. In children, who are its more frequent vic tims, it is generally only noted that they do not hear or that they are not talking as they should. Convulsions without de fined or protracted illness may be re ported as the starting-point, or trauma with loss of consciousness. The deaf ness following mumps may belong in this category, but generally seems rather an acoustic paralysis.
Autopsies in cases of cerebrospinal fever where there had developed deafness bar(' ritam, which revealed destructive tissue-changes in the internal ear. The processes were suppuration and necrosis. The probable cause is a direct action of the morbid virus upon the capillaries of the periosteum,—and pre-eminently in the semicircular canals,—producing vas cular stasis and thrombosis in this mem brane, with consequent necrosis of the structures thereto attached. Stein brugge (Archives of Otology, vol. xvii, p. 51, 'SS).
Two cases of total loss of hearing in both ears consequent upon mumps. One patient had suffered from purulent otitis; the other ease presented normal mein brame tympani. In such cases the lesion is located within the labyrinth. Barr (Glasgow Med. Jour., June, 'S9).