III. On the structure and function of the rods of the cochlea in man and other mammals

The ear is, it is well known, one of the most complicated organs of the body, consisting of the external, middle, and internal sections, the two former being concerned in collecting and conducting sounds or vibrations, while the duty of the internal portion consists in receiving, localizing, and clearly distinguishing them. It is simply with this last 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. 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 of this spiral, there proceeds horizontally a plate of bone, the lamina spiralis, almost dividing this canal into two; from this plate, again, there extend two membranes, the membrane of Reissner and the lamina spiralis membranacea, as far as the walls of the canal, thus separating it into three minor canals. Between the layers of the membranous spiral lamina are situated the so-called Rods of Corti. These were first discovered and described by the Marquis de Corti; and although since then many observers have studied the subject, yet scarcely two investigators are agreed as to their exact form.