GROWTH OF THE INNER EAR OF ALBINO RAT 



41 



In table 10 the radial breadths of the whole membrane and 

 of its zones are arranged accordingly to the turns of the cochlea 

 on age. At the bottom of each column are given the ratios 

 from 1 to 546, 12 to 546, and 20 to 546 days. We see at first 

 that the total radial breadth at one day is largest in the basal 

 turn; at three days it becomes larger on passing from the basal 

 toward the II and III turns, but in turn IV it is again small. 







25 



50 



50 100 200 300 400 500 



Chart 7 The radial breadth of the membrana basilaris, table 9, figure 2, 

 distance 11. 



Total radial breadth of the membrane. 



Radial breadth of the zona pectinata. 



Radial breadth of the zona arcuata. 



After six days it is a well-known fact that the radial breadth of 

 the membrana basilaris is narrowest in the basal, and widest 

 in the apical turn (not the tip of the apex, but the beginning 

 of the apical turn). These differences are not always the same 

 between all the turns; those between I and II, and II and III 

 are marked; those between III and IV are small. The ratios 

 at 1 to 546 days show those for the upper turn to be largest, 

 while from 12 to 546, and 20 to 546 days the ratios in all turns 

 are about 1:1.1. 



