138 ARRANGEMENT AND STRUCTURE OF SUSTENTACULAR CELLS 



of development the summit of the cell body becomes lengthened out into its segment 

 of support; the paraxial filament, at the level of the nucleus, courses obliquely 

 through the lateral part of this segment and gives off another branch the axial 

 filament thus expanding into a fibrillar chalice located within the wall of the cup- 

 shaped depression. 



13. Contrary to the opinion of many authors, the columnar epithelium of the 

 greater epithelial thickening of the cochlea duct does not undergo disintegration 

 during the development of the sulcus spiralis. At the level of the latter no cells are 

 lost, but all become flattened out to cover the greatly extending furrow. Near the 

 organ of Corti the columnar cells persist longer, and occasionally exhibit evidences 

 of chromatolysis. 



14. Medial to the inner mixed row of hair-cells there exists a second row of 

 inner sustentacular elements with differentiated apices. These resemble in many 

 respects the cells of Deiters of the third outer row, although in the course of devel- 

 opment the cell bodies of the latter are shifted beneath and support the neighboring 

 acoustic elements. Like the sustentacular cells of the first inner row, those of the 

 second remain in their original row; the apices of both take part in the formation of 

 the membrana reticularis, that is, the apparatus of support of the apices of the hair- 

 cells. Hence they represent true sustentacular elements. Like the cells of Deiters 

 of the third row, the sustentacular elements of the second row also represent 

 boundary elements. 



15. Among the so-called cells of Hensen there exists, lateral to the third row of 

 cells of Deiters, a fourth outer, mixed row, formed of alternating atrophied susten- 

 tacular cells and more superficial hair-cells. The atrophied hair-elements become 

 shorter in the course of development, but persist, even in the adult cochlea. As a 

 rule, the absence of nerve fibers seems to result in atrophy of the constituents of this 

 fourth row, but in man these become normally developed. 



16. From the earliest stage of development the cytoplasm of the hair and sup- 

 porting cells contains innumerable chondriomites and chondrioconts which, by their 

 peculiar arrangement, give rise to a longitudinal striation. By their aggregation 

 the chondriosomes form the body of Retzius and the body of Hensen, each one rep- 

 resenting a center of developing chondriomites, whence the chondriomites migrate 

 into other portions of the cell. The superficial body of Hensen is closely connected 

 with the cuticula of the hair-cell. This superficial plate is derived from coarse, 

 coalescing chondriomites which appear to undergo a chemical alteration. Hence 

 the hairs arising from the cuticula should be regarded as of mitochondrial origin. 



17. The outer and inner rods of Corti and the cells of Deiters contain a fibril- 

 lated framework which, from the earliest stages of development, appears in the form 

 of mitochondrial bands or strands. Each fibril is the result of fusion of the super- 

 posed chondrioconts. In addition to the sustentacular function of the framework, 

 these elements possess also a function of nutrition. Indeed, the bulk of their 

 cytoplasm is clear, and contains, besides a few chondriosomes, a serous fluid which 

 exudes from the subjacent vas spirale and permeates the protoplasm of the cells in 



