GROWTH OF THE INNER EAR OF ALBINO RAT 



75 



and while the spiral organ is enlarging, the inner hair cells, and 

 therefore the organ, may be moved in the apical coil of the 

 cochlea axialward a distance of about half the maximum width 



of the greater epithelial ridge, " 



The differences of the values in the rat at 9 and 546 days are 

 in the basal and apical turn about the same, 39 and 36 n, res- 

 pectively (table 44). Thus while the inner edge of the inner 

 pillar cell approaches at 546 days in the basal turn by as much 

 as 41 per cent of the distance present at nine days, that in the 



80 



M- 

 60 



40 



20 







o 



25 



50 



50 100 200 300 400 500 



Chart 20 The vertical distance from the membrana basilaris to the surface 

 of the pillar cells, table 46, figure 1, 1-1. 



apex moves only 20 per cent inward in old age. This result 

 is the reverse of that obtained in the pig by Hardesty. The 

 reason for this contradiction I will discuss later. 



10. The vertical distance from the membrane basilaris to the 

 summit of the pillar cells. The method of getting the vertical 

 distance from the membrana basilaris to the surface of the 

 pillar cells is shown in figure 1, line 1-1. In table 46 (chart 20) 

 are given the values thus obtained. At the foot of the last 

 column are given the ratios of this distance at 1 to 12, 1 to 20, 

 1 to 546, 12 to 546, and 20 to 546 days. The average value is 

 relatively large at birth, it diminishes at three days, then increases 

 more rapidly to twenty days. After this it decreases very slowly. 

 The maximum height of the arch of Corti is at twenty days of 



