GROWTH OF THE INNER EAR OF ALBINO RAT 63 



6. The radial distance between the habenula perforata and 

 the outer border of the foot of the outer pillar cell. The deter- 



. mination of this distance is deemed necessary not only as a datum 

 on growth in general, but also for its bearing on the difficult 

 question of the shifting of the outer pillar cell, to be discussed 

 later. On the other hand, this distance is identical with the 

 radial length of the zona arcuata of the membrana basilaris 

 (table 7. inner zone). 



In table 35 (chart 14) are given the values for the radial 

 distance between the habenula perforata and the outer corner 

 of the outer pillar cell at base. At the foot of each column are 

 given the ratios at 1 to 12, 1 to 20, 1 to 546, and 20 to 546 days. 

 As table 35 shows, the distance increases continuously from birth 

 to old age, rapidly up to twelve days, but later gradually. Up 

 to three days the distance is slightly larger in the lower turns, but 

 after this age the relation is reversed, and this persists through life. 



The increasing ratio of the distance for each turn according 

 to age is smallest in turn I and largest in turn IV. The ratios 

 for the condensed data are given in table 36. While the ratio 

 at birth is the same in each turn, 1:1.0, that of turn I to II is 

 smallest for every condensed age. Also it is to be seen that the 

 increase of the ratio in turn I to II is smallest and that in turns 

 I to IV is largest. In Retzius' work ('84) we find the following 

 values for this distance (table 37). 



Table 37 shows that in the rabbit the growth changes are 

 similar to those in the rat, though the absolute values are somewhat 

 larger. As in preceding determinations, the values for the cat 

 do not stand in the same relation as those for the rabbit, but 

 indicate precocity. Some corresponding observations by Hensen, 

 Bottcher, and others will be presented later. 



7. The greatest height of the greater epithelial ridge {der grosse 

 Epithelwulst {Bottcher) s. Organon Kollikeri) resp. of the inner 

 supporting cells {fig. 4, G)> The so-called greater epithelial ridge 

 is a prominence formed by high cylindrical pseudostratified cells. 

 It is situated axialward on the tympanic wall and continued 

 outward to the lesser epithelial ridge. About the fate of this 

 ridge there were various divergent opinions among the older 



