The Nature of tlie Tectorial Membrane 111> 



out into filaments of less than half the diameter of the original 

 membrane and which seem to have lost all trace of elasticity. These 

 filaments may be drawn asunder and the parts will remain with 

 tapering" and pointed ends. Pieces of membrane from cochleae fixed 

 in Zenker's fluid show a slight increase in rigidity and therefore greater 

 elasticity when the slight strains are applied, but, if stretched further, 

 they break with a transverse cleavage instead of suffering permanent 

 attenuation. In the study of the structure of the membrane it was 

 foimd that the lines of such cleavage follow the direction of the filu-ous 

 components of the membrane. 



The tectorial membrane suffers severely in the presence of all reagents 

 which are hypertonic to it. Most all the recent papers touching upon 

 its structure admit that it undergoes shrinkage with treatment for 

 embedding and sectioning. I made several careful attempts to pre- 

 pare pieces of the memlirane for mounting in balsam so as to get 

 more permanent and probably more transparent preparations, but none 

 were successful. However carefully the graded alcohols were applied, 

 by the time dehydration was complete, the membrane would show 

 shrinkage, constrictions and general distortion, and a bath in xylol 

 would usually complete what the alcohols had begun. Eesults some- 

 what lietter were obtained by clearing with creosote after 95 per cent 

 alcohol, but no preparations so made would bear comparison with the 

 normal, mounted direct in glycerine, either as to shape, dimensions, 

 evenness of contour or surface markings. The physical character of the 

 membrane seems to be such that it is impenetrable to the alcohol 

 molecule, or at least such that it cannot be dehydrated without 

 shrinkage. 



Under the dissecting microscope by reflected light it has a distinct 

 glassy appearance and by transmitted light it is transparent. The 

 compound microscope shows it to consist of fine colorless fibers 

 embedded in a transparent matrix. This matrix has apparently tlie 

 nature of a glutinous, collagenous semi-solid. It is hardened but slightly 

 by fixing fluids containing no alcohol. It is about the first structure 

 in the cochlea to be affected by maceration, for cochleae taken from 

 pigs not freshly obtained show evidences of liquefaction of the tectorial 

 membrane Avhen the organ of Corti may be practically intact. Sections 

 of such cochleffi show above the organ merely a mass of tangled filaments 

 resembling a coagulum. On the other hand, the membrane seems to 

 be more readily fixed than the organ, for sections of cochlea pronounced 



