306 O. VAN DER STRICHT 



of Deiters of the third row, which remain in situ between the 

 third row of sensory elements and the cells of Hensen, will 

 appear the large fourth interstice. 



Before the appearance of any space the phalanx process is 

 composed of a clear cytoplasmic sheath, enclosing a darker, 

 axial, mitochondrial strand, which by juxtaposition and fusion 

 of the chondrioconts becomes gradually transformed into an 

 axial, fibrillated filament. The process is larger at its base, 

 which issues from the nucleated cell body, and tapers to the 

 superficial membrana reticularis. 



In a kitten nine days old, at the level of the apical spiral 

 turn of the cochlea, the second, third, and fourth sustentacular 

 interstices are still filled up with the unmodified phalanx proc- 

 esses, so that intercellular spaces are absent. In the- second 

 turn, narrow channels appear and are somewhat larger near the 

 surface of the epithelium than towards the base of the processes. 

 Inversely the processes have become reduced in diameter at the 

 expense of their clear protoplasm. At the level of the basal or 

 third turn the enlargement of the spaces of Nuel and the re- 

 duction in size of the cytoplasmic sheath of the phalanx proc- 

 esses are much more marked. It must be noted that the 

 thinning out of the latter is not the result of a sheer concomitant 

 elongation, for these alterations are accompanied by a con- 

 siderable elongation of the nucleated cell bodies of the sus- 

 tentacular elements, involving a subsequent shortening of the 

 supported hair cells, hence of the neighboring phalanx processes. 

 These become more slender on account of a process of elabora- 

 tion and secretion and a subsequent extrusion of clear fluid 

 from the protoplasmic sheath. Whether, as many preparations 

 seem to prove, this discharge is accompanied by a process of 

 true cytolysis is uncertain, for these structures are very delicate 

 and the shrinkage caused by the reagents might give rise to 

 artefacts liable to misinterpretation. 



The fourth space of Nuel de^'elops in the same manner as the 

 second and third, and when it appears, is but little larger than 

 the others. It is occupied by the apical processes of the ceUs 

 of Deiters of the third row. Originally as long as the neigh- 



