On the structure and function of the rods of the cochlea in man and other mammals / by Urban Pritchard, M.D.

  • Pritchard, Urban.
Date:
[1873]
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Licence: Public Domain Mark

Credit: On the structure and function of the rods of the cochlea in man and other mammals / by Urban Pritchard, M.D. Source: Wellcome Collection.

Provider: This material has been provided by The University of Glasgow Library. The original may be consulted at The University of Glasgow Library.

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    in. On the Structure and Function of the Rods of the Cochlea in Man and other Mammals. By Urban Pritchard, M.D., F.R.C.S., Demonstrator of Physiology, King's College, London. (^Rewi bpfore the Medical Mioroscopicat. Society, Feh. 21, 1873.) Plate XIIT. Befoee entering upon the description of the rods themselves, it may be well to refer briefly to the mechanism of the ear, and the method by which we are able to hear and distinguish certain sounds. The ear itself, as is well known, is one of the most complicated organs of the body, consisting of the external, middle, and internal sections: the two former are merely concerned in collecting and conducting sounds or vibrations; while the duty of the internal portion consists in receiving, localizing, and, moreover, clearly dis- tinguishing them. Now, it is simply with this last and most dehcate function of the organ that I purpose to deal, my aim being to describe the true construction and use of the cochlea so far as its task of distinguishing the various sounds is concerned. I may state that, for convenience sake, I shall in the course of my remarks speak of the cochlea with its apex uppermost. This cochlea, it must be borne in mind, consists of a spiral canal, in form and shape very similar to the inside of a snail-shell. From the axis, or modiolus as it is called, of this spiral, there proceeds horizontally a plate of bone, the lamina spiralis, which almost divides this canal into two. From this plate again there extend two membranes to the walls of the canal, thus separating it into three minor canals. Of these two membranes the upper one or membrane of Eeissner (Fig. II.) arises just behind the teeth of the limbus (as the peripheral end of the bony lamina is called), and passes upwards and outwards to the upper part of the Ugament of the cochlea; it is exceedingly dehcate, and is composed of a- single layer of flattened nucleated cells, closely adhering to each other, and which are situated on a very thin membrane. EXPLANATION OF PLATE XIIL Fio. I.—The upper extremities of the roils (dog), showing the mode of articnln- tion and processes. Drawn by camera, x 500 dinm.; /, inner rod; o outer rod. „ II. - A diai/ramatic drawing of a vertical section of the central canal of the cochlea, x about 150 diam. 1. Scala vestibuli. 2. Central canal of cochlea. 3. Scala tympani. A, Membrane of Eeissner ; B, Mnmbrnna tectoria; 0, Bony liimina spiralis; D, Membrana basilaris; E Liga- ment of cochlea ; F, Nerve plexus ; G, Epithelium ; II, Membrana reticularis; L, various cells; f, inner rod; o, outer rod. „ III.—Three pairs of rods carefully drawn from three sections of the cochlese of the same nnimal (cat), showing the mode of graduation—I, from near the apex of cochlea; 2, from about the middle; 3, from near the base