450 C. AV. PRENTISS 



membrana shrinks shows that its normal position has been dis- 

 turbed. We may as logically assume that it was attached and 

 in many cases has shrunken away as to assume that it floated 

 just parallel to the surface of the spiral organ and has become 

 pressed down upon and attached to it by coagulations. 



We may assume this even more logically for we hold, and our 

 preparations and dissections and the observations of Held {'09) 

 prove absolutely that the membrana is attached to the epithelial 

 structures of the spiral organ in late fetal stages. There is no nec- 

 essity for, and my preparations afford no proof of, an inward 

 shifting of the spiral organ and a consequent displacement of 

 the membrana. It is therefore unnecessary to assume with 

 Hardesty and Von Ebner ('02) that any attachment between 

 membrana and spiral organ must be of secondary development. 



While these arguments against the existence of an attachment 

 between the membrana and spiral organ may be readily answered 

 it is none the less true that a complete attachment to the cells 

 of the spiral organ, such as exists in the fetus, has never been 

 demonstrated in the adult organ. Nor, to my knowledge, has 

 it been explained why the membrana should detach itself so 

 readily from the spiral organ yet always retain its attachment 

 to the labium vestibulare. First, as to the reason the complete 

 attachment may be demonstrated in the early fetus and not in 

 the adult: This is probably because the attachment is more firm 

 in the fetus and because the basal epithelium and the basal 

 membrane are less rigid in the fetus and tend to shrink pari passu 

 with the membrana. In the adult or even the new-born young 

 the tissues are less watery, more rigid and more resistant to 

 reagents. The basilar membrane is attached to the bony laby- 

 rinth, now strongly ossified. The membrana alone shrinks to 

 any great extent and as a result is more or less completely torn 

 away. 



Why the membrana should always lose its connection with the 

 spiral organ and not its attachment to the labium vestibulare is 

 explained by its structure. Over the labium it is an almost solid 

 cuticular structure and the few chambers in this region are flat- 

 tened and contain little fluid. Over the spiral sulcus the mem- 



