DEVELOPMENT OF THE MEMBRANA TECTORIA 449 



flexible it would naturally sink downward and away from the 

 spiral organ assuming that it was not attached to the cells of 

 the latter. This would be all the more apt to occur when the 

 membrana is subjected to the heavy jars incident to active 

 movements, running and jumping, and should interfere with 

 hearing. As we know, such interference does not occur. 



The arguments raised by Hardesty against any normal attach- 

 ment of the membrana, save to the labium vestibulare, are : 



1. In dissecting the fresh membranous labyrinth to expose the 

 membrana its outer portion could be seen floating free along its 

 entire extent. 



2. In the majority of sections it is entirely free from the spiral 

 organ and when attached such attachments are filamentous and 

 may be explained as abrasions of the under surface or coagula- 

 tions of precipitated albumins. 



3. ''From the process of its development it seems probable 



that the membrane is free from the underlying 

 structures," and as its outer zone acquires its position over the 

 spiral organ by displacement, one must assume that any attach- 

 ment which exists between the membrana and the spiral organ 

 must have developed secondarily. 



Hardesty's first argument bears little weight because in de- 

 scribing his method of studying the fresh membrana tectoria he 

 states that it was necessary to crush the bony labyrinth with a 

 hammer and that the disturbances caused by his dissection caused 

 the membrana to float free from the labium vestibulare an attach- 

 ment which is never entirely ruptured in carefully fixed sections. 

 A method which would destroy the strong attachment to the 

 labium would certainly set free the more delicate attachments 

 to the spiral organ. 



Moreover, dissections which were made by using more favorable 

 methods did not seem to support Hardesty's observations. As 

 to the attachments seen in sections being artifacts it is sufficient 

 to say that I have traced the hairs into the membrana in many 

 cases and that attachments to the inner supporting cells and to 

 the outer hair cells are so strong as to distort the spiral organ 

 during the shrinkage of the membrana. The very fact that the 



