PROPORTIONS OF THE TECTORIAL MEMBRANE 3 



and fetuses in the paper of the writer and in papers by others 

 appearing since. These points made it desirable to again go 

 over from the beginning the processes by which the tectorial 

 membrane and spiral organ are developed. As bearing upon 

 these points, it is deemed allowable to review here certain steps 

 in the development as now found by the writer, and some draw- 

 ings illustrating these steps are given. 



Another purpose for which this paper is submitted is that it 

 is a necessary anticipation qf the study, begun earher, involving 

 the construction of the model mentioned above, with a view to 

 illustrating the possible action of the membrane as a vibratory 

 mechanism in the process of hearing. A description of the 

 results of this attempt is now in preparation. 



In my previous paper, using freshly obtained cochleae of pigs at 

 and near 'term,' it was found that by very tedious and careful procedure 

 it was possible to remove by teasing methods parts of and even the 

 entire tectorial membrane in the fresh state. In the fresh state, the 

 membrane was found to be most inconceivably flexible in nature, 

 to cohere and to adhere to the teasing instruments with a most exas- 

 perating readiness, and to have a specific gravity practically no greater 

 than that of the fluid in which it normally lies. It is transparent and 

 its removal was best accomplished over a black stage of the dissecting 

 microscope. Its behavior in the fluid in which it was teased under the 

 dissecting microscope indicated that the fresh membrane possesses 

 barely enough elasticity against stress applied to it transversely to 

 enable it to gradually assume its coil when floating about in the fluid 

 l)efore coming to rest upon the bottom of the dish. Once in contact 

 with the bottom it could not resume its coiled character. On the 

 other hand, it appeared to possess considerably more elasticity against 

 stress applied parallel with its length, more than enough to enable it 

 to maintain its shape in transverse section and certainly enough to 

 maintain its outspanning position just over the hair cells of the spiral 

 organ, whatever the position of the head. 



Under the compound microscope, study of both its whole thickness 

 and of torn bits showed it to consist of very numerous fine filaments 

 embedded in a seemingly gelatinous matrix. The membrane being 

 of ectodermal origin, the matrix was considered as a jelly-like form of 

 keratin. The varying directions, length and independent character 

 of the filaments was described and the various other features of the 

 membrane which seemed evident to the writer were compared as they 

 agreed with or differed from the findings of others recorded in the liter- 

 ature. It was further found by experiment that the action of certain 

 fixing fluids of themselves, those containing no alcohol and whose 



