102 



AYERS. [Vol. VI. 



plate." He was not able to find any sort of cavities within the 

 middle zone such as Waldeyer described. The figures on its 

 lower surface, stripes, polygonal figures, are without doubt im- 

 pressions of the surface of the structures on which it lies. The 

 major part of the membrane of Corti is contained in the middle 

 zone, which is fibrous. Its fibres are of very peculiar composi- 

 tion, long, for the most part undulating (in surface view), and 

 very fine. They are especially soft, extensible, and very elastic 

 in nature, so that the whole membrane has the nature of a soft, 

 elastic mass. 



Corti's membrane is, notwithstanding the contrary views of 

 Hensen and Waldeyer, very elastic, and this peculiarity agrees 

 well with its probable physiological function as a damping 

 membrane. Its elasticity as a mass is due mainly to the inter- 

 fibrillar substance, which Boettcher saw, and which Lavdowsky 

 found was composed of inter-fibrillar granules. This substance 

 easily swells up, and in so doing small vacuoles appear, in which 

 condition Corti's membrane presents the appearance of a gelat- 

 inous, almost mucous mass. This substance is not found in 

 the other parts of the membrane, e.g. in the outer zone. This 

 zone is entirely homogeneous, still more elastic than the middle, 

 which, explains its more frequent distortion and displacement 

 and rolling together. He could not accept Hensen's view as 

 correct for the normal position of the membrane. He had 

 nothing to add to Hensen's account of the hyaline border net 

 nor the row of knobs. 



Krause (1876) described the inner hair cells as bearing ex- 

 tremely finely pointed hairs. The outer hair cells differ from 

 the inner in that they have an oval capsule entwined in a spiral 

 nerve fibre, placed between the nucleus and hair-bearing cell 

 cap. 



Pritchard (1878, 217). In his account of the development of 

 the organ of Corti, Pritchard says that, on the whole, Corti's 

 pillars, the membrana reticularis, and the vertical trabeculse 

 have been developed out of the walls of the epithelial cells, 

 while the Jiair-bearing and all other cells have developed from 

 the contents of the original epithelial cells. 



The membrana tectoria is a cuticular secretion of these cells. 



Pritchard (1881, 216) described the auditory apparatus of Or- 

 nithorhynchus platypus and compared it with that of ordinary 



