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Dr. U. Pritchard on the Structure and 



[May 30, 



nation of the kind as to make it a matter of much interest that a larger 

 number of meteoric irons from various localities should be subjected to 

 careful examination in the same direction, thus supplementing our know- 

 ledge of the fixed constituents of these curious bodies by a study of their 

 gaseous contents, 



III. " On the Structure and Function of the Rods of the Cochlea in 

 Man and other Mammals." By Urban Pritchard, M.D. 

 Communicated by Prof. Lionel Beale, M.D. Received April 

 18, 1872. 



(Abstract.) 



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 sepa- 

 rating it into three minor canals. 



Between the layers of the membranous spiral lamina are situated the 

 so-called Rods of Corti. These w r ere 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. 



Deiters has published the results of two investigations, in w r hich the form 

 of the rods is differently described ; Kolliker, Henle, and others appear to 

 agree with Deiters's later view, and most of our text-books have copied 

 their drawings. Recent writers, such as Dr. A. Bottcher, AYaldeyer, &c, 

 give varying drawings, some of which are nearer the true form of the rods 

 than that of Deiters, while others exhibit them in all kinds of extraordinary 

 shapes. 



In a general view of the rods from above, they appear similar to two 

 rows of pianoforte-hammers, rather than like the keys of that instru- 

 ment, to which they have been likened. In a lateral view, these two rows 

 of rods are seen sloping towards each other, like the rafters of a gabled 

 roof. The rods consist of a shaft and two enlarged extremities, but the 

 two rows differ considerably in form ; the inner rods are attached by their 



