PROPORTIONS OF THE TECTORIAL MEMBRANE 5 



membrane. In transverse sections of the membrane, this immediate 

 surface appears as a darker rind, or so condensed that the filaments 

 cannot be traced in it, and it was referred to as the 'peripheral con- 

 densat'on.' A peripheral condensation likewise appears on the basal 

 surface of the membrane in sections of embedded cochleae. There 

 it was usually thinner and less uniform than on the convex surface 

 but was considered as representing the last and likewise incomplete 

 product of the activity of the cells producing the membrane — the 

 surface left as the cells were ceasing to function and were being torn 

 away from their product in receding from it. The appearance of con- 

 densation, or the darker rind, was considered as due to the action of 

 the reagents upon the different character of these surfaces. 



The basal surface of the removed membrane, viewed on the 13at, 

 showed three lines. The axial one of these was found to be the line 

 of the imprint of Hiischke's teeth, or the line marking the outer margin 

 of the attached axial edge (inner zone) of the membrane. The middle 

 line was found to be 'Hensen's stripe,' a surface marking described 

 by Hensen in 1863. This stripe was decided to be a very shght 

 linear elevation occurring coincident with the line of the interlocking 

 phalanges of the pillars of the spiral organ and thus adapted to the 

 groove or space on the surface of the organ between the hairs of the 

 inner and outer series of hair cells. A peripheral or outer line ap- 

 peared to be the line of attachment of the outer margin of an other- 

 wise detached or detachable thin layer of the basal surface which was 

 described as an "accessory tectorial membrane." In the apical coils, 

 this line, or outer edge of the accessory membrane, runs considerably 

 axial to the outer edge of the tectorial membrane. This distance 

 however gradually decreases towards the basal coil till the line comes 

 to coincide with the outer edge of the tectorial membrane, or, in other 

 words, the outer edges of the two membranes gradually come to co- 

 incide toward the basal end. The evidence of the existence and the 

 description of the structure of this accessory membrane as well as the 

 description of the arrangement of the filaments in the membrane proper 

 were presented in some detail. 



As to the attachment of the tectorial membrane, it was shown that 

 the membrane is purely a cell product, wholly non-cellular from its 

 beginning; that during its formation it is of necessity attached to the 

 cells which produce it, and, at any stage of its formation, an incom- 

 pletely formed region must be and is then attached to the cells com- 

 pleting that region; that its thin axial edge or zone, the region whose 

 production ceased earliest, remains permanently adherent upon the 

 vestibular lip of the spiral limbus; but that, after its production is com- 

 pleted, by actual observation of it in position in teased specimens and 

 in trustworthy sections of it, by the study of the later stages of its for- 

 mation b}'^ the cells concerned, and from the change in position of the 

 spiral organ with reference to its basal surface, the conclusion was 

 reached that the main body or entire outer zone of the membrane 

 does, and by necessity comes to, project entirely free over the spiral 



