DEVELOPMENT OF THE ORGAN OF CORTI 305 



but unquestionably disappears by a process of cytolysis in the 

 adult bat (fig. 13'' ^ 14 and 15, oph''') and the white rat (fig. 17). 

 Evidences of such disintegration are shown in figures 9 and 10 

 (cy). The result is that a part of the clear cytoplasm which 

 belongs to the originally enlarged heads of the outer pillars 

 (fig. 8, ohd) undergoes a process of liquefaction. A portion of 

 the intracephalic horizontal fibrillar band becomes free or at 

 least partially destitute of protoplasm, so that the fluid of the 

 large space of Nuel, in direct communication with that of the 

 tunnel space through the wide interpillar clefts, comes in close 

 contact with the very fine, superficial, fibrillated membrane of 

 the head of the inner pillars. This membrane separates the 

 fluid in question from that of the cochlea duct. 



The -physiological importance of these structures is evident, 

 for the vibratory waves may be readily transmitted from one 

 to another fluid through the intermedium of the striated mem- 

 brane. As regards the transmission of vibrations from the- 

 fibrillated basement membrane of the membrana basilaris to the 

 contents of the first interstice of Nuel, it is noteworthy that 

 the fonner, at the level of the floors of the Nuel and tunnel's 

 spaces, is separated from the latter by only a very thin cyto- 

 plasmic covering which belongs to the laterally expanded feet 

 of the outer pillars and to the feet of the outer and inner pillars. 

 Hence the transmission can be readily carried out. 



Development of the second, third, and fourth spaces of Nuel. As 

 shown in previous investigations, the phalanx processes of the 

 cells of Deiters of the first and second rows are represented, in 

 the earliest stage of development, by long apical segments of 

 the cell bodies, which segments are included, respectively, in 

 the second and third row of outer hair cells, within which they 

 run between two neighboring acoustic elements. In length 

 these apical segments agree with the hair cells. Due to the 

 rapid enlargement of the latter, the apical segments are pressed 

 out from their original row and shifted into interspaces; those 

 of the first row of Deiters cells reaching the second future inter- 

 stice of Nuel and those of the second row of Deiters cells reaching 

 the third interval. All around the phalanx processes of the cells 



