438 c. ^y. prentiss 



In describing a 14 cm. stage Hardesty says: ''Up to this stage, 

 the membrane never overlaps the lesser thickening and in confirma- 

 tion of the statement of Rickenhacher it must be said that at no 

 stage is there good reason to assume that the cells giving rise to the 

 organ of Corti ever have anything to do with its development."^ 

 Rickenbacher in his summary states that ''Die Cortische mem- 

 bran ist somit doppelten Ursprungs: Die innere Zone ist die 

 primare welche von grossen Epithelialwulst abgeschieden wird. 

 Die schmale Randzone ist eine sekundiire Bildung, welche an 

 dem kleinen EpitheUalwulst abgesondert wird." As Ricken- 

 bacher states that the outer portion of the spiral organ is devel- 

 oped from the lesser 'Epithelial-wulst' and the inner portion from 

 a part of the greater 'Epithelialwulst,' the above quotation is not 

 in accord with Hardesty's statement. Rickenbacher's figures 

 (11, 12, 13) show the membrana developing over the cells 

 of the spiral organ and attached to the hairs, so also do the 

 figures of Held ('09) and even in Hardesty's figure 10 the mem- 

 brana is shown projecting beyond the outer pillar cells and 

 attached to the inner cells of the spiral organ. On dissecting 

 away the membrana at this stage it was found that the thin 

 platelike zone, overlying the spiral organ, and extending beyond 

 it was no artifact due to coagulation, but a definite structure of 

 the same appearance and continuous with the rest of the mem- 

 brane. The total width of this membrana was found to be 

 equal approximately to that of the membrana in the same turn 

 of a 18.5 cm. stage. 



In our descriptions we have referred heretofore to the struc- 

 tures composing the membrana tectoria as 'lamellae or fibers.' 

 From the manner in which these are attached to the cells and 

 from horizontal sections it will be seen that such terms can not 

 rightly be applied to them. Sections of the membrana cut 

 through the cochlea perpendicular to the modiolus or axis show 

 their true significance. In such a section the organ of Corti 

 (spiral organ) and the limbus are cut at right angles to the long 

 axes of their cells, the line of section being indicated by x in figure 



• Italics mine. 



