42() C. W. PRENTISS 



From the physiological standpoint it is then necessary to 

 answer two anatomical questions before we may assign the mem- 

 brana a logical role in the processes of audition: (1) Has the 

 membrana any definite and peculiar structure w^hich may adapt 

 it to the transmission of sound vibrations? (2) Is the membrana 

 so attached as to be constantly in contact with the hair cells 

 of the spiral organ? We hold that as yet these questions have 

 received no adequate answer. 



The membrana is described by nearly all of those who have 

 investigated it, as being an elastic cuticular structure containing 

 within its interstices a more or less fluid matrix. This cuticular 

 membrane has been variously interpreted as formed of aggluti- 

 nated ciha or hairs (Ayers '92); as lamellar (Shambaugh '07); 

 as a reticulum (Retzius '84); as a coagulum of the endolymph 

 (Czinner and Hammerschlag '98) ; as a fibrous feltwork embedded 

 in a gelatinous matrix (Hardesty '08) ; as composed of fibers and 

 cuticular layers (Held '09). 



As to its attachments there is a division of opinion, some 

 holding that it is attached to the spiral organ (Retzius '84, Coyne 

 et Cannieu '95, ffishi '07, Shambaugh '07) while this is denied 

 by others — more recently by Rickenbacker ('01), Hardesty ('08) 

 and Held ('09). 



The classic figures given in textbooks of anatomy and histology 

 (fig. 1) show it as a lamellated membrane attached to the labium 

 vestibulare and extending outward over the internal spiral sulcus 

 and the organ of Corti. Its outer edge thus floats free in the 

 endolymph and the lamellae are shown parallel to the ends of 

 the hair cells. The textbooks usually state that it takes its 

 origin from the limbus spiralis and hence must grow by the 

 development of new lamellae from beneath. 



The conclusions of those who have worked on the development 

 of the membrana tectoria are as contradictory as are those who 

 have interpreted its structure. Kolliker ('61) originally de- 

 scribed the membrana tectoria as a finely striated membrane 

 arising from the columnar epithelial cells of the basal wall of the 

 ductus cochlearis. Hensen ('63), Retzius ('84), Pritchard ('78), 

 Schwalbe ('87) and others agree as to its cuticular origin. Czinner 



