GROWTH OF THE INNER EAR OF ALBINO RAT 



73 



and 12 to 546 days of age. As the table shows, the values in- 

 crease in general from birth to nine days; therefore, the surface 

 of the greater epithelial thickening from the labium vestibulare 

 to its outer boundary becomes, during the earlier stage, wider 

 and wider, then decreases sharply, and after that continuously 

 but slowly. This sudden diminishing of the distance has a very 

 intimate relation with the change in the form of the papilla 

 spiralis at this stage of development. 



This point I will discuss later. 



That the values increase from the base to the apex first rapidly 

 and later less rapidly, is also to be seen here. Table 45 shows this 

 relation clearly. It is remarkable, however, that the ratio becomes 



140 



12O 



1OO 



AGE DAYS' 



25 



50 50 1OO 2OO 300 400 50O 



Chart 19 The radial distance between the labium vestibulare and the 

 inner edge of the head of the inner pillar cell, table 44. 



at each turn larger with age, although the absolute value is 

 after nine days generally smaller than at the preceding age. 

 Therefore, we see that the diminution of the distance after 

 nine days is largest in the basal turn and smallest in the apical. 

 Hensen ('63) asserts that there is a movement axialward of 

 the organ of Corti (resp. the head of the pillar cell), but gives no 

 measurements. Neither Bottcher nor Retzius measured this 

 distance. Prentiss ('13, page 445) states that "the distance 

 between the inner angle of the cochlea and the pillar cells, two 

 definite points, may be measured with considerable accuracy 

 and shows no important change in the position of the spiral 

 organ from the 13 cm. to the 18.5 cm. stage, nor later in the 

 new born animal" (pig) But he also does not record his meas- 

 urements. 



