GROWTH OF THE INNER EAR OF ALBINO RAT 17 



part near the base. This transparent area is not the locus of 

 the future tunnel of Corti, but marks the protoplasmic change 

 into the pillar, as the transparent substance condenses into the 

 rod. We can see this change beginning in the basal turn before 

 it appears in the apical turn of the cochlea. The inner and 

 outer cells make a triangle with a narrow base, which clings to 

 the membranea basilaris; they turn somewhat outward. 1 



A large oval nucleus lies in the basal part of each cell ; that of 

 the inner pillar cell is very large, about twice as large as that 

 of the outer, and with its long axis in a radial direction. As 

 figure 4 shows, the inner corner of the inner pillar cell does not 

 yet reach to the habenula perforata. 



The hair cells, which in the albino rat are in four rows through 

 all the turns, are separated by the pillar cells into two groups, 

 the inner containing one and the outer three rows of cells. They 

 are comparatively well developed at birth (fig. 4). The inner 

 hair cell belongs to the greater ridge, as Kolliker ('67), Gottstein 

 (72), Retzius ('84), Held ('09), and others have already affirmed, 

 and contrary to the assertaion of Bottcher ('69) and others. 



It is situated in the most outer part of the declivity of the 

 greater ridge and slants away from the axis with its round lower 

 end at about half the height of the greater thickening. It has 

 a large round nucleus in the base and the small hairlet at the top. 

 This hair cell is nearly twice as large as the outer hair cells. 

 The three outer hair cells reach down to the middle of the lesser 

 ridge, not through it, having no process at their basal end. 

 They end with their upper parts at the surface of the prominence. 

 They stand not straight, but turn with their long axis very 

 slightly inward, i.e., the in direction opposite to the long axis 

 of the inner hair cells. They are cylindrical in form with a round 

 nucleus at their base and small hairlet on the top. 



Below the outer hair cells stand the three rows of Deiters' 

 cells, which have large oval nuclei. These rest with their wide 

 bases on the basilar membrane and their pointed ends reach 

 to the surface of the epithelium. They are retarded in develop- 



1 In the following description of the cochlea, 'outward' means away from the 

 axis 'inward' towards the axis. 



