100 AYERS. [Vol. VI. 



true of the third zone which unites with the border process 

 further outward. Hensen's knobs are considered by Boettcher 

 to be the remains of the connection of the membrana tectoria 

 with the inner hair cells. Boettcher claims still in defending his 

 earlier view that the membrana tectoria is tensely drawn in a 

 radial direction, and calls attention to a homogeneous inter- 

 fibrillar substance which lies between the isolable fibres. The 

 membrane is elastic in a direction perpendicular to the course of 

 the fibres and must be much more so in a radial direction. The 

 only certain knowledge we have of nerve endings in the cochlea 

 was gained from cross-sections in which the nerve fibres were 

 seen to fuse with the inner hair cells. Of the longitudinal 

 nerve fibres, he says : " Die longitudinalen Fasern werden nicht 

 eher anerkannt werden, als sie auf den Durchschnitt demon- 

 strirt sein werden. Das hat noch Niemand gethan, ja es hat an 

 einen solchen sogar noch Niemand die Stelle angeben konnen, 

 wo sie liegen." He calls attention to the possibility of con- 

 fusing these spiral nerve fibres with the cell elements on the 

 lower surface of membrana basilaris. 



Hensen (1873, 33) concluded, after an examination of Boett- 

 cher's preparations, that his supposition was incorrect, that 

 Loewenberg's reticulate lamella played a role in the formation 

 of the membrana tectoria. 



In Boettcher's preparations taken from embryos of the cat 

 there extended from the membrana Cortii (which did not lie 

 upon the membrana reticularis), out over the small ridge, a 

 thin membranous plate. Below this membrane were fibrous 

 structures, which were doubtless artifacts. This membrane, 

 present in embryos, disappears later. The reticular membrane 

 found over Corti's membrane (discovered first by Loewenberg) 

 has nothing to do with the inner zone in guinea-pig and rabbit, 

 but simply passes out over it, becomes very thin, and ends 

 freely. Concerning the physical peculiarities of the membrana 

 Cortii, Hensen does not agree with Boettcher that it is very 

 elastic in radial direction, especially since we know nothing of 

 its elasticity. He contradicts Boettcher's observations that the 

 membrana tectoria is radially tensely stretched and that it con- 

 tracts when broken loose. 



After experiments instituted for the purpose, Hensen con- 

 cludes that the consistency of the membrana tectoria lies 



