Contributions to medical science / by Alexander Ogston.

  • Ogston, Alexander, 1844-1929
Date:
1869
Catalogue details

Licence: Public Domain Mark

Credit: Contributions to medical science / by Alexander Ogston. Source: Wellcome Collection.

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    with the cochlea, and having a cavity distinct from that of the utricle. The cochlea, the other portion of the internal ear, consists of a spiral tube divided into two passages of equal size by a partition running along its whole length, so as to separate the two passages from each other, except at the top of the spiral where they communicate, while the other ends of the tubes are attached, one to the foramen rotundum, being closed off by a membranous partition from the middle ear, and the other to the saccule, foramen ovale, and stapes, being thus in connection with the chain of bones in the middle ear and with the drum of the ear. These spiral passages are filled with fluid. It will be perceived that the cochlear portion of this apparatus alone possesses a direct and obvious connection with the middle and external ears, and correspondingly it is found that as the external ear disappears in animals the cochlea disappears also. The distribution of the auditory nerve corresponds more or less with this anatomical arrangement, the cochlea being supplied by one separate branch, and the contents of the vestibule and semicircular canals by another. From the whole of this arrangement it would appear as if the cochlea were the organ destined chiefly to receive impressions communicated from the external auditory meatus through the drum and chain of bones, and as if the contents of the vestibule and semicircular canals had a function quite separate and distinct from this. But before leaving the anatomy of the ear, it is necessary to call attention to the fact that the size of the arched canals varies in different individuals, and that their amplitude and development differ much in different animals, even of the same genus, being, for example, according to Agassiz and Gould, “ broad and elevated in rapacious and passerine birds, and thick and depressed in the grallse, gallinse, and palmipedes.” Doubtless, the varying development bearsj an intimate relationship to the habits and requirements of the animal, and a careful study of this relationship could not fail to throw much light upon the function of the part. In considering the different properties which sound possesses with a view to arranging these properties into some sort of classification, we find that the ear is capable of distinguishing the varying intensity or loudness of sound, distance of sound, direction of sound, pitch or tone as in the different musical notes, and other peculiar qualities of sound as exemplified in the peculiarity of the violin notes, in contrast, say, with those of the harp. Of these, the first two, intensity and distance, are probably one and the same thing; the ear judging of the distance by the intensity ; and this reduces the properties of sound as appreciated by the ear to four heads : 1st, Intensity ;