DEVELOPMENT OF THE MEMBRANA TECTORIA 



439 



5. That portion of the membrana extending o\'er the sulcus is 

 seen cut perpendicular to the fibers or lamellae (fig. 7). 



Its structure is that of a reticulum. The meshes are composed 

 of delicate cuticular walls and at their angles are triangular or 

 rectangular thickenings. The walls of the network are sharply 

 defined and in unstained preparations appear highly refractive 

 and clear. This structure can not be due to the effects of fixing 

 reagents upon a gelatinous substance for in this case the lines 

 of strain would not be as definite and would have a grayish, 

 granular appearance instead of being clear and refractive as is 



Fig. 7 Membrana tectoria sectioned in a plane perpendicular to the axis of the 

 cochlea, thus cutting across the 'fibers.' The drawing shows its reticular structure 

 with thickenings at the angles of the meshes. From a fetus of 15 cm.; ep., epithe- 

 lium. Oc. 2, 2 mm. Obj., t. 1. 160. 



Fig. 8 Diagram showing structure of the membrana tectoria as proved by 

 figures 4 to 7; r., reticulum, as seen in horizontal sections; I., 'lamellae' or 

 'fibers,' seen in axial sections. 



the case with this cuticulum of the membrana tectoria. The 

 spaces enclosed by the network correspond in form and size to 

 cross sections of the epithelial cells and where "the membrana 

 approaches the epithelium may be seen to correspond to the 

 ends of the cells. The structure of the membrane is thus neither 

 lamellar nor reticular but 'cellular' in the sense that honeycomb 

 is cellular. The cuticular portion of the membrane corresponds 

 to the waxen cells and these chambers are closed during develop- 

 ment by the ends of the epithelial cells. There is this difference 

 in the comparison that while the 'cells' of a honeycomb are nearly 



