AND THE CRISTA SPIRALIS OF THE COCHLEA. 61 



In figure 2 are displayed the same details in a transverse, slightly oblique section 

 of the second turn of the cochlea in a pig embryo (93.5 mm.). The lesser epithelial 

 ridge is barely indicated (Ir) by a superficial mosaic (ml) , of which all the polygons 

 belong to indifferent epithelial cells, although below them are seen three special nuclei 

 (ns) separated by a considerable distance from others more deeply situated (nsu). 

 This superficial location of the nucleus is the first sign of sensorial differentiation 

 in an epithelial cell. The deep nuclei belong to future supporting cells. The 

 superficial mosaic of the greater ridge is visible (mg), and just at its lateral or outer 

 side is a row of five fields, three larger (ih) separated by two smaller (is), three 

 apices of future inner hair-cells separated by two apices of future inner supporting 

 cells. The outer hair-cells appear later. Toward the axial part of the greater ridge 

 exist three mitotic figures (mi) located below the superficial mosaic; they are the 

 last existing traces of the proliferation zone of Baginsky (1886), which is very well 

 marked in earlier stages. 



Figure 3 represents a transverse, slightly oblique section of the greater (gr) 

 and lesser (Ir) ridges on the second turn of the cochlea in a new-born dog. N. Van 

 der Stricht (1908) describes many similar figures in his photos 42, 42', 44, 45. I 

 will emphasize only the details reproduced on a greater scale in figure 4, a section 

 tangential to the surface of the two epithelial ridges. These confirm for the dog 

 the description given by N. Van der Stricht of embryonic bats, as shown in his 

 photo 52 among others. 



From the axial towards the outer region of the two ridges in figure 4 are the 

 following: 



1. The superficial mosaic of the greater ridge (mg), the most lateral polygons of 



which are differentiated into one row of circular inner sensorial fields, the 

 apices of the inner hair-cells (ih) regularly separated by compressed elon- 

 gated narrow fields, the apices of the inner supporting cells (is). 



2. A row of small polygons, the apices of the inner pillars (ip). 



3. A first row of apices of outer hair-cells (oh') separated by the phalanges of the 



outer pillars (op). 



4. A second row of apices of outer hair-cells (oh") separated by the phalanges of 



the first row of Deiters cells (d'). 



5. A third row of apices of outer hair-cells (oh'") separated by the phalanges of 



the second row of Deiters cells (d"). 



6. The apices of the third row of Deiters cells in the form of small polygons (d'") 



similar to those of the inner pillars. 



Figure 5 is from a segment between the second and third turns of the same 

 cochlea and shows identical structures. But there exists a fourth row of outer 

 hair-cells (o/i lv ) and a fourth row of Deiters cells (d' v ) along a very small portion 

 of the cochlea. Retzius (1884) states that the organ of Corti in the rabbit and the 

 dog exhibits a fourth row of outer hair-cells in the superior part of the middle turn 

 and along the largest part of the apical turn. Waldeyer (1872) mentions a fourth 

 row in man and Retzius (1884) confirms this, but adds that the fourth row and 

 even a fifth belong to the upper part of the cochlea and are largely interrupted. 

 I must point out that the outer sensorial fields of the recently differentiated part 



