PROPORTIONS OF THE TECTORIAL MEMBRANE 33 



Upon looking at Held's figures of his Decknetz I felt sure at 

 fxrst that he was describing the structure I referred to as an acces- 

 sory tectorial membrane with its regularly arranged fibrils washed 

 together and cohering in irregular bundles, making his net, and 

 that either he had mistaken it to be on the apical surface or I 

 had been mistaken in thinking it on the basal surface of the 

 tectorial membrane. In his description of it and in his figures, 

 the outer border of his Decknetz is shown to be thicker and its 

 meshes finer than in other parts. The 'accessory membrane' 

 might appear thus if its fibers were disarranged by the treat- 

 ment. He thinks the 'bars' of his net are assembled from finer 

 fibrils and states that the direction oi the bars in places conforms 

 with the direction of the fibrils in the fibrillar IsLjer or main 

 body of the membrane below. However, he describes his 

 Decknetz as extending on the apical surface of the membrane 

 from and usually involving its outer edge, over the entire outer 

 zone and upon the axial or inner zone which is attached upon 

 the vestibular lip of the spiral limbus. While one of the two 

 systems of fibers in my accessory membrane appeared to con- 

 form with the direction of the fibers in the main body of the 

 tectorial membrane, the latter being crossed at very acute angles 

 by the other system, only in the basal turn did the outer edge 

 of the accessory membrane seem to extend to the outer edge of 

 the main body, and only in the basal turn did its very delicate 

 axial edge seem to me to extend further axisward than the line 

 of Hensen's stripe. As seen by Held, his Decknetz is consider- 

 ably wider. He states that he could not follow it completely 

 over the attached axial zone because of the density of this region. 



Held's homogeneous layer bounding the basal surface of the 

 tectorial membrane is, I think, nothing more than the finely 

 granular and faintly fibrous pale staining layer found by Ricken- 

 bacher ('01) for the guinea-pig after decalcification with nitric' 

 acid and staining with eosin. After the procedure used by me, 

 both in the previous and in the present studies, to obtain sec- 

 tions of the membrane, the stain I used shows a thin more densely 

 staining layer bounding both the apical and basal surfaces. I 

 described this as a peripheral condensation of the substance of 



THE AMERICAN JOURNAL OF ANATOMY, VOL. 18, NO. 1 



