4 IRVING HARDESTY 



ingredients produced no appreciable exosmotic diffusion currents in 

 tissue elements, caused very slight distortion of the membrane. In 

 Zenker's fluid, for example, the endosmotic and exosmotic effects 

 upon the membrane appeared to be quite evenly balanced and measure- 

 ments of the dimensions of tectorial membranes after its action indi- 

 cated that practically no differences from the dimensions of the fresh 

 had been produced. Cochleae could be left in this fluid long enough 

 for decalcification of the fetal bony lamina and thus allow much greater 

 ease and precision in removing this from the membranous cochlea 

 preliminary to clipping the latter away in order to remove the tec- 

 torial membrane. After Zenker's fluid, the membrane in the fetus 

 at term appeared more opaque, less flexible, less fragile, and more easil}^ 

 i-emovable entire from its attachment upon the vestibular lip of the 

 spiral limbus. Such fixed specimens could be washed in water, but 

 attempts to dehydrate and clear them always resulted in shrinkage 

 and distortion. Mounts for study had to be made in glycerine or 

 glycerine-jelly. 



Measurements of both the fresh and the thus fixed tectorial mem- 

 branes gave an average length of the membrane, in pigs at about 

 term, of 25.5 mm. In width and thickness it was found to decrease 

 gradually and evenly from its end at the apex of the cochlea, where 

 it is much the largest, to the narrow and thin end of its basal coil, which 

 ceases to project in width beyond the hair cells of the spiral organ. In 

 the first or apical coil, the width of the membrane was found to be 

 such that its outer edge projects considerably beyond the outer hair 

 cells of the organ. 



In extent, the tectorial membrane was found to occupy the coch- 

 lear duct throughout and to be strictly coextensive with the spiral 

 organ. Thus its length is less than the lengths of the scalae on its 

 either side, especially less than that of the scala tympani. Each of 

 its ends was found to l)e rounded and to terminate bluntly. Its axial 

 edge thins suddenly and knife-like and is permanentl}' attached upon 

 the vestibular lip of the spiral limbus, being left thus attached by the 

 ectodermal cells, \vhich, at an early stage, ceased to produce it, leaving 

 it adherent to the fibrous mesenchymal tissue comprising 'Buschke's 

 teeth' and the remaining portion of the vestibular lip covered by it. 

 Its outer edge was found to be bluntly rounded and slightly scalloped, 

 as a result of the component filaments curving apex-ward around this 

 edge from the basal surface, and frequently in small bundles, to form 

 the edge. The apical surface was found to be convex and smooth. 

 The immediate convex surface consisted of a thin layer representing the 

 result of the first activity of the then young producing cells below, 

 in which layer or first product the matrix at least had not been so 

 completely produced as later, allowing the first formed ends of the 

 filaments to become tangled or washed, as it were, into an irregular 

 arrangement resembling a reticulum. The remainder of the filaments 

 continued into the body of the membrane, untangled and evenly em- 

 bedded in the later and more completely produced matrix of the 



