An American text-book of diseases of the eye, ear, nose and throat / edited by G.E. De Schweinitz and B. Alex. Randall.

Date:
1899
Catalogue details

Licence: Public Domain Mark

Credit: An American text-book of diseases of the eye, ear, nose and throat / edited by G.E. De Schweinitz and B. Alex. Randall. Source: Wellcome Collection.

Provider: This material has been provided by the Harvey Cushing/John Hay Whitney Medical Library at Yale University, through the Medical Heritage Library. The original may be consulted at the Harvey Cushing/John Hay Whitney Medical Library at Yale University.

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    impression. With the binaural conduction of sound there appears to be an alternating; centric increase of sensation upon the two sides.1 There is not only a close homology, but a functional relationship, between the auditory and the visual centers of the quadrigemina. Acoustic stimula- tion of the posterior body leads to a quite apparent increase of irritability in the cells of the anterior body, and to such a degree that more distinct visual sensations, especially in the color-field, are induced.- The functions of sound-perception, of auditory judgment, and of auditory memory are localized in the cerebral cortex. In a portion of the first and second temporal convolutions lying ventral to the Sylvian fissure, and in direct communication with the auditory sensation-centers of the basal ganglia3 by fiber-tracts which pass in both directions,4 lie the centers which constitute the auditory brain. These cortical functions have to do with the analysis and synthesis of sound, with the recognition of rhythm, with the determination of distance, and sound-location, and with the recollection and re-creation of sounds previously registered. The remarkable development of the faculties of sound-analysis and synthesis in certain individuals predicates a high order of specialization in this seat of the musical mind. The judgments of sound- distance and location are largely instructed by a comparison of the sensations begotten of impressions made, simultaneously or alternatingly, upon the two sides. In the estimate of distance the intensity of a sound is a governing and an often misleading guide. Thus a low, feeble sound produced in the near neighborhood will often convey the impression of distance, and vice versd. In making up the judgment of distance it is not so much the total intensity as the intensity of the component elements of a sound which gives the most correct conclusions (Bloch). The location of a sound is almost wholly dependent upon binaural hear- ing. Bloch has shown that it is more readily determined in the horizontal and frontal planes than in the sagittal plane. A comparison by the nerve- centers of the several characteristics of intensity, continuance, pitch, and qual- ity in the sounds received by the organs of hearing; upon the two sides is the major factor in the case. The degree of sound-collection achieved by the two auricles is a minor influence in informing the judgment of the locality of a sound. The function of sound-memory is but imperfectly developed in the major- ity of persons, while in a very few individuals it reaches a high degree of per- fection. The existence of a memory-center for auditory perceptions, apart from the temporal centers of sound-perception and judgment, is undemon- strated. Any tendency to dogmatic statement in regard to the specific functions of auditory centers is arrested by the promise of new light which is suggested by the recent investigations of Kolliker, v. Lenhossek, and Held into the origins of the auditory nerve-fibers, and by the late demonstration by Ramon y Cajal of a new auditory nucleus in front of the convexity of the upper olivary body. 1 Bloch : Archives of Otol., xxiv. 2. 2 Epstein: Zeitsehr.f. Biol., xxxiii. N. F., B. XV. :l Starr: Op. clt. 4 C. v. Monakow: Arehivf. Psyehiatrie, Bd. xxvii.