150 



ANATOMICAL AND PHYSIOLOGICAL STUDIES ON 



TABLE 113 — Concluded 

 Diameter of nuclei of the inner and outer hair cells 



values are marks of maturity. These changes in size accord 

 with the results given in chapter 1 at twelve days of age, though 

 there are some differences between them in the absolute values. 



Figures 7 and 8 illustrate the outlines of the tympanic wall 

 of the membranous cochlea in nine-day-old rats which could 

 not and could hear, respectively. These figures have been 

 drawn from the corresponding sections at the beginning of 

 the middle turn of the cochlea and are comparable with figures 

 3 to 6 and 9 to 12. On comparing figures 7 and 8, the more 

 noticeable differences appear to be the following. 



The membrana tectoria is a bit -longer in the hearing rat. 

 The appearance and the position of it with reference to the 

 surface of the papilla spiralis is also different. In the not-hearing 

 cochlea it has an infantile look. 



The outer end of the main part does not yet reach the second 

 row of the outer hair cells and connects with the Hensen's 

 prominence by a thick thread. There are also many fine fibers 

 to be seen between the basal surface of the membrane and the 

 papilla. In the hearing rat the fine fibers are absent. The 

 membrane reaches already the row of the outer hair cells and 

 there is a strong connection between this part and the terminal 

 ame (Schlussrahmen) of the lamina reticularis by a thick 



read as shown in figure 8 Thus the position of the membrane 



