AND THE CRISTA SPIRALIS OF THE COCHLEA. f)7 



taking up the same stain. But around and between the cells one sees an alveolar 

 system, on optical sections a network of blue (if stained by Mallory's method) or 

 green (if impregnated by light green) collagenous sheets or filaments in continuity 

 with the basement-membrane. Within the spaces of the reticulum sections of the 

 protoplasmic prolongations of the cells are visible. The alveoli, large in the deep 

 layers, become gradually smaller in the neighborhood of the columnar epithelium. 

 The superficial epithelium is represented by a row of prismatic cells, the nuclei 

 of which may be situated at various heights. Each cell contains a single nucleus 

 and the intercellular spaces are closed by the terminal bars already mentioned. 



2. The second stage is that of the beginning proliferation of the connective 

 tissue between the epithelial colls. Figure 12, from a photograph of the second 

 turn of the cochlea in a 127.0 mm. pig embryo, shows this process in vertical sec- 

 tion. The basement-membrane (6m), more or less visible on the right toward the 

 future zona papillaris, has disappeared toward the left near the sulcus spiralis (essp), 

 where the proliferation first begins and is always most advanced. There exist 

 below the epithelium larger alveolar spaces, and the constituents of the membrane 

 with the collagenous elements of the connective tissue extend between the bases 

 of the epithelial cells in the form of dark intercellular filaments. At first sight this 

 intraepithelial connective substance seems to be homogeneous and no transverse 

 sections of bundles are perceptible. Upon careful observation, however, it shows 

 very small spaces within which thin prolongations (pr) of connective-tissue cells are 

 detected. Hence it must be recognized that from the first stage of proliferation cell- 

 prolongations and collagenous walls or sheets penetrate between the epithelial 

 elements. Tangential sections of the crista spiralis demonstrate that this prolifera- 

 tion is performed in such a way that the epithelial cells are pressed together in 

 more or less parallel rows along the future zona dentata (fig. 13, zd). The axis 

 of the cellular rows (ep) is also parallel to the surface of the limbus and is directed 

 from the future vestibular lip toward the zona papillaris. No collagenous sub- 

 stance exists between cells of the same row. Figure 12 proves that neighboring 

 epithelial cells of the greater ridge, which later will cover the sulcus spiralis (cssp), 

 participate in this alinement and special arrangement of the epithelial elements. 

 These very small parallel intraepithelial connective sheets (ic, fig. 13) represent, 

 of course, the future teeth of Huschke, which in oblique tangential sections (t, fig. 

 14) are clearly in continuity with thicker subepithelial parallel septa of the same 

 nature (st, fig. 14). Consequently, it is obvious that this intraepithelial arrange- 

 ment in the form of teeth of Huschke is in the first place induced by a special and 

 similar disposition of the subepithelial substratum. 



3. The distinctive feature of the third stage is that the connective-tissue teeth 

 are more or less as large as the interdental epithelial sheets. Vertical sections of 

 the crista spiralis in a pig embryo of 127 mm. stained by Mallory's method show 

 this fact (fig. 16). Each superficial epithelial cell (ep) seems to contain two or 

 three nuclei (owing to the oblique direction of the section) and to be cylindrical; 

 but the red-stained cytoplasm at its free surface is in continuity with a similar 

 email superficial layer (mcr), dark in the photograph, covering the intermediary 



