The jSTature of the Tectorial Membrane 127 



peculiarities of the difficult regions sketched in. The sketch was then 

 transferred to a sheet of Eoss-board, upon which it was thought advisable 

 to make the attempt to represent the glassy, delicately fibrous character 

 of the membrane as it appears over a black surface. Figs. 2, 3, 4 and 

 5 were outlined in the same way, but under higher magnification, and 

 are intended to show greater structural detail. 



Measurements of the thiclcness of the membrane could be obtained 

 only from vertical sections of cochlese made after the usual fixing, 

 dehydrating and embedding. After getting some idea of the character 

 of the membrane, a few specimens, carefvilly treated and embedded in 

 celloidin, gave sections which showed considerably less shrinkage and 

 distortion than is usually evident. Figs. 6, 7 and 8 were outlined 

 from photographs of and drawn from a section of one of these specimens. 



All the membranes showed some distortion and shrinkage. The latter 

 especially is evident in a denser and more amorphous shell-like thicken- 

 ing about the entire periphery, which suggests a primary condensation 

 due to the first attack of the shrinking agent, and which, once formed on 

 the periphery may be less permeable and may result in the interior por- 

 tion being subsequently more gradually and therefore less violently acted 

 upon by the reagents. Fig. 8, from the seventh half -turn or basal coil, 

 shows decided distortion and displacement due to shrinkage. This is 

 from the more slender jjortion of the membrane, and, if the above sug- 

 gestion is true, would necessarily be affected most by the reagents. 



Measurements of the thickness taken from these specimens and cor- 

 rected with the study of the isolated and supposedly unshrunken pieces 

 indicate two relations : 



(1) That, like the width, the thickness of the membrane begins with 

 that of the outer zone in the rounded end at the apex (see Fig. 1), 

 rapidly increases to its maximum in the apical region and thence gradu- 

 ally decreases toward the basal coil, in the end of which the minimum 

 thickness occurs. 



(2) That, throughout, the line of the greatest thickness, in the 

 different transverse sections, runs approximately parallel to the edge of 

 the labium vestibulare and approximately over or slightly to the inner 

 side of the line of the enclasped phalanges of the rods of Corti. 



The measurements of thickness were all taken from sections of the 

 cochlefe of pigs at or very near term. They gave the following average 

 tliir-kup-^sos for the regions specified: 



