96 AVERS. [Vol. VI. 



ing away of Corti's membrane. The third zone of the mem- 

 brane is sharply marked off and begins with a hyaline border ; 

 then follows a network of fine trabeculae with regular openings. 

 The membrana tectoria is not, as Boettcher at first thought, 

 united with the ligamentum spirale. 



Boettcher correctly describes how the tectorial membrane 

 develops with reference to the length of the cochlea. In pig 

 embryos of 7 cm. length he found the membrane well developed 

 in the second half of the first and in the first half of the second 

 spiral turns, while both above and below this it gradually fades 

 out, and is thus in harmony with the stage of development of 

 the hair cells of these parts of the cochlea. 



Winniwarter (1870, 292) says Corti's membrane shows three 

 zones, the innermost thin, resting on the auditory ridge, very 

 delicate, faintly striate, from occasional perforations presenting 

 an imperfect netlike appearance and occasionally marked on 

 its under surface by the outlines of epithehal cells which seem 

 to be like those of the auditory ridge. The second zone begins 

 at the end of the teeth, is striated diagonally from within and 

 above, downwards and outwards, the striation being due to sep- 

 arable fibres. This zone ends outwardly in a border, rounded 

 below, which is characterized by a hyaline edge. In the middle 

 of this zone a dark line runs through the fibrous mass. The 

 outer zone is composed of a network of structureless, anastomos- 

 ing, hyaline meshes, the fibres of which arise from a hyaline 

 edge. A more profusely branching plexus passes centrad over 

 the surface of the membrana tectoria, extending far over the 

 middle of the middle zone. The membrane is very resistant 

 and elastic. It extends outwards certainly to the outer border 

 of the three rows of the outer cells of Corti. The connection of 

 the inner and outer pillars {Stege ttnd Saitcn) is a very firm 

 one. There are about twenty-nine inner to thirty-eight outer. 



Grimm (1870, 105) found the length of the hairs of the cristas 

 acusticse to be 0.035 mm., while the cells were only 0.025 mm. 

 high. The nerve fibre passes to base of cell ; the axis cylinder 

 pierces the wall, runs to the nucleus, on to the hair cap mem- 

 brane, which it passes through, and ends in the base of the 

 hair as a knob of stainable substance (black in osmic). 



Hensen (1871, 129) corroborated Boettcher's observation that 

 the inner and outer pillars of Corti are composed of fibres. He 



