GROWTH OF THE INNER EAR OF ALBINO RAT 



15 



In table 3 are given the average ratios between two radial 

 distances between I-II and III-IV at four ages. Here we can also 

 see a rapid increase in the ratio from one to eight days of age, 

 while afterwards the ratios rise very gradually. The data in 

 table 2 show that at nine days the mean diameter of the bony 

 cochlea as thus measured is approximately 97 per cent of the 

 value at maturity. The cochlea thus attains nearly its full size 

 at an early age. Chart 1 illustrates this point. 



Chart 1 The radial distance between the spiral ligaments, turns I-II and 

 III-IV, table 2, figure 3 (/-/) and (-). 



Radial distance at turns I-II. 



Radial distance at turns III-IV. 



Average radial distance for the two foregoing measurements. 



All the charts are plotted on age. 



The scale for age changes at 50 days. From to 50 days one interval is 

 equal to five days. From 50 days on, one interval is equal to twenty-five days. 



Unless otherwise stated, the measurements recorded in these charts have 

 been made on radial-vertical sections. 



