GROWTH OF THE INNER EAR OF ALBINO RAT 



43 



In the zona arcuata (inner zone) the same relation is to be 

 seen in each turn; therefore, in the early period the breadth 

 is less in turn IV than in the other turns. Very soon, however, 

 the value in turn IV becomes the largest and diminishes toward 

 the base. The rate of the growth of this zone, from 1 to 546 days, 

 is also smallest in turn I, and largest in turns III or IV; the 

 ratios being in the first 1:1.6, and in the last 1:2.1. 



In the zona pectinata (outer zone) we see also similar relations. 



TABLE 11 



Ratios of the radial breadth of the membrana basilaris according to the turns of the 



cochlea on age 



Only slight differences in the ratios according to age are found. 



In table 11 the ratios according to the turns of the cochlea 

 are given. While from one to three days the ratios are the same 

 in each turn, 1:1.0, yet after six days those for turns I to II are 

 smallest, and for I to IV larger, thus showing slight differences 

 between them. 



In the literature we find only one description, that by Retzius 

 ('84) touching the growth of the radial breadth of the membrana 

 basilaris according to age. He measured this membrane in the 

 rabbit and cat and got the following values in n (table 12). 



