70 THE GENESIS AND STRUCTURE OF THE MEMBRANA TECTORIA 



third plane (nb). They are more or less parallel in the zona dentata and anasto- 

 mosed in the zona papillaris (zp, fig. 22). In preparations from the pig embryo 

 they are stained rosy by Congo red, and in those from the bat they are faintly blue 

 from iron hematoxylin, the nuclei being dark blue. The nuclear bands are larger 

 than the cytoplasmic. 



The teeth of Huschke (t) between these epithelial sheets are clear and homo- 

 geneous in figure 22, like the papillse of the zona papillaris (2;;). But in figure 23 

 the teeth are striated from the presence of long granular filaments stained faintly 

 blue, the prolongations of subjacent connective cells. The fundamental substance 

 of the teeth is stained rosy by Congo red. 



Transverse compared with tangential sections permit one to conclude that in 

 the adult crista spiralis the interdental epithelial sheets (lamellae) are much longer 

 than in previous stages and reach a deeper level in the subjacent connective- tissue, 

 but that they remain in direct continuity with the superficial cytoplasmic mosaic, 

 covering entirely the surface of the teeth and the papilla?. Beneath this mosaic their 

 transverse diameter is the smallest, while in their deeper nuclear portion it remains 

 practically the same as in the preceding stage or decreases a little. This elongation 

 and thinning of the sheets is due to a broadening and mechanical pressure of the 

 intermediary teeth. 



The reduction in size and in number of nuclei of the epithelial lamellae is shown 

 much better by the tangential sections than by the transverse. This change, 

 more apparent than real, may be imputed to their elongation in a direction parallel 

 with the axis of the primitive cell and undoubtedly to the wide extension of the 

 sheets during the increase in size of the crista spiralis. But comparing figures 22 

 and 23 (where long cytoplasmic bands separate two rather small nuclei) with figures 

 18 and 19 (where the neighboring nuclei are in close contact) it seems to me that 

 during the development of the limbus spiralis an increase of the cytoplasmic mass 

 occurs and can not be denied. 



This consideration brings me to the important question of study of the epithe- 

 lial lamellae of the crista spiralis; all authors describing vertical sections of this 

 admit the existence of separated cells, the primitive epithelial cells. Indeed, figures 

 12 and 13 prove that during the first and second stages this view is correct, and 

 figures 16, 20, and 21 seem to confirm it for the third and fourth stages. All sections 

 tangential to the surface of the crista, however, show different figures. At the third 

 stage (figs. 17, 18, 19) no boundaries between cell-areas can be detected either in the 

 cytoplasmic or in the nuclear bands where the nuclei are very closely pressed to- 

 gether. This statement is also true for the fourth stage (figs. 22 and 23). Conse- 

 quently these epithelial sheets must be considered as real syncytial masses formed 

 by fused epithelial cells, which are separated only during the first and second stages 

 of their development. This fusion is brought about by a mechanical factor, the 

 compression from the broadening teeth. This multinuclear syncytium is unex- 

 ampled in other organs, while here the primitive apices and central corpuscles of 

 the epithelial cells persist intact, the boundaries being marked by the terminal 

 bars. Retzius (1884) and N. Van der Stricht (1908) refer to similar figures, but 



