186 THE AUDITORY NERVE AND COCHLEA, BY W. WALDEYER. 



granules. In the retina it is evident that differentiation has been 

 carried to a greater extent at this point ; the rods may therefore be 

 the analogues of the external hair cells, and the cones of the internal 

 hair cells. At any rate, the relations of the nerves indicate some- 

 thing of this kind, for we find that relatively thick fasciculi of axis- 

 fibrils run to the inner hair cells just as they do to the cones, 

 whilst to the outer hair cells, as to the retinal rods, only fine indi- 

 vidual fibrils run. Whether any physiological differences also exist 

 between the internal and the external hair cells, as Max Schultze has 

 demonstrated in the case of the rods and cones, may be fairly sus- 

 pected. The thick cuticle of the lamina reticularis is without homo- 

 logue in the retina, unless we compare it with the limitans externa, 

 against which view serious objections might at present be raised. 



The spiral fibrous bands (c, fig. 835A) of the organ of Corti are 

 obviously analogous to the intergranule layer, and the auditory granule 

 layer (d) to the internal granule layer of the retina ; at least, the 

 entire microscopic relations of these two strata are for the most part 

 similar. The ganglion-cell layer, represented by the ganglion spirale, 

 is in the case of the ductus cochlearis removed to some distance from 

 the preceding structures, and there is consequently a less marked 

 homology with the molecular layer of the retina, which, perhaps, we 

 may consider to be represented by the fine plexiform connective 

 tissue which surrounds the auditory fibres from the ganglion to the 

 entrance into the foramina nervina. 



In comparing the two structures together collectively, it must be 

 borne in mind that the elements of the retina are for the most part 

 arranged perpendicularly to one another, whilst those of the organ of 

 Corti, so far at least as regards the group of the external hair cells, 

 are arranged upon the same plane, like those of the retina at the 

 yellow spot. 



Structures corresponding to the lens and the vitreous humour cannot 

 be looked for. I am quite aware how incomplete this comparison 

 must for the present remain. I have, however, been desirous to 

 sketch it, since, by prolonged researches in this direction though 

 doubtless morphological and physiological identity are often far apart 

 we may expect to obtain some important knowledge to aid in the 

 comprehension of the auditory labyrinth, 



CONTROVERTED POINTS ; HISTORICAL NOTICES. 



In view of the differing statements of various observers already 

 given, we must here limit ourselves to the consideration of such 



