PROPORTIONS OF THE TECTORIAL MEMBRANE 47 



cells begin to recede along the axial side of the ridge and the 

 ridge begins to decrease in width, the last produced ends of the 

 fibrils are drawn axisward in the basal surface of the membrane. 

 This drawing axisward is done only by the cells of the thicker 

 and more persistent outer part of the greater ridge, the drawing, 

 I think, extending in the basal surface only about as far axisward 

 as Hensen's stripe, which it helps to form as well as helping to 

 form the basal peripheral condensation as seen in the sections. 

 The fibrils thus drawn axisward must form the arrangement on 

 the basal surface of the outer part of the teased out membrane 

 described by me as an "accessory tectorial membrane." 



The increase in the number of cells in the greater ridge during 

 its increase in width results, of course, in an increase in the 

 number of fibrils and thus in the width of the membrane as com- 

 pared with the earher stages. If the claim made by Prentiss 

 that the tectorial membrane is a honey-comb or chambered 

 structure, each chamber coinciding with and produced by a 

 cell, were true, then in the sections would be found occasionally 

 strips as wide as the cells, walls of the chambers parallel with 

 which the plane of section had passed. Such strips have never 

 been seen. On the contrary, the fibrillar character is one of 

 the most evident possessed by the membrane. 



In sections in which the condition similar to that shown in 

 figure 10 could be seen, the region of junction (/) appeared 

 fighter than the earlier formed part of the membrane. This is 

 interpreted as indicating that the interfibrillar matrix here has 

 not, as yet, been completely formed. Figure 11 represents the 

 condition, some degree of which is the usual appearance in all 

 sections of dehydrated cochleae while the membrane is being 

 formed. It is interpreted as the result of the action of the 

 reagents, used in the preparation for sectioning, upon the last 

 and not yet perfectly formed part of the membrane. The matrix 

 in this region must be in a stage more readily shrunken by de- 

 hydration and clearing than in the earlier formed part of the 

 membrane. The fibrils appear agglutinated into kregular 

 bundles with spaces between them more or liess free. In the 

 area drawn the bundles were formed for the most part, one on 



