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O. VAN DER STRICHT 



fibrillated bundles, the rootlets of the fibrils of the phalanx 

 process and the apical ends of those of the pillar body, 

 respectively. 



5. The original head of the inner pillar is represented by a 

 small, four-sided, somewhat flattened prism. Later by com- 

 pression from the outer pillar's head, the superficial part of the 

 prism assumes a more distinctly lamellar shape; the lower part 

 enlarges and acquires its largest size at the level of the lower 

 pole of the outer pillar's head, whence it tapers upward and 

 downward. The so-called 'head' of the inner pillar extends 

 down beyond that of the outer and furnishes a pad of support 

 to the latter. The prismatic head is composed of a lateral uniform 

 cytoplasm, which enlarges at the level of the lower, broader 

 portion, and a medial fibrillated lamella. In contact with the 

 obturator septa and within the homogeneous protoplasm the 

 head collar develops. 



6. By compression from the underlying and enlarging head 

 of the outer pillar, the free apex of the inner pillar undergoes a 

 gradual and extensive elongation, becoming converted into a 

 fibrillated, long head-plate. The constant position of the 

 central corpuscle within this niembrane, close to the apices of the 

 outer hair cells of the first row, proves that this elongation 

 occurs in a definite direction, from the seat of the diplosome 

 toward the apices of the inner hair cells. 



7. The heads of the outer pillars are asymmetrical in structure. 

 The cephalic notch, imperfectly surrounded by the head cap, is 

 traversed by two fibrillated bundles and has a parapical posi- 

 tion; it is situated nearer to the apical surface of the head (i.e., 

 the surface turned toward the apex of the cochlea) than to the 

 basal, since the apical lip of the groove is thinner than the basal. 

 The horizontal rootlets of the fibrillated phalanx bundle are also 

 parapical and merge obliquely into the apical border of the 

 notch. The vertical fibrillar cephalic bundle, arising from the 

 pillar body, divides into two unequal fasciculi, a smaller and 

 a larger, circumscribing a cleft through which run the horizontal 

 fibrils. The smaller fasciculus merges into the apical lip of the 

 notch and the larger one into the basal lip, the bulk of the head 

 cap. 



