130 ARRANGEMENT AND STRUCTURE OF SUSTENTACULAR CELLS 



In transverse sections of the cells the cytoplasm apears granular, the filaments 

 being cut across (fig. 9, oh 1 , oh", oh 1 "). Due to their presence, the protoplasm, 

 even in specimens where the mitochondria are not stained, is always compact 

 and dark. In the cochlea of the white rat, before birth and also two days after 

 birth, these chondriosomes stained red by fuchsin and the nuclei green by methyl- 

 green, after fixation by a mixture of formalin and bichromate. 



Densely accumulated and packed chondriomites give rise to coarser structures, 

 the so-called body of Retzius, the body of Hensen, and the superficial cuticula and 

 hairs. The presence of the body described by Retzius (1884, p. 366) as "eine 

 grdssere, kornig erscheinende Protoplasmaansammlung," has been confirmed by 

 Held (1902), N. Van der Stricht (1908), and Kolmer (1909), in the outer hair-cells. 

 It exists within these elements in white rats before birth and in other new-born 

 mammals (fig. 1, oh) in the form of a deeply staining granular mass of chondrio- 

 mites, which incloses in its concavity the lower pole of the nucleus. In later stages 

 of development (fig. 21, oh', oh") the subnuclear, cytoplasmic portion of the hair- 

 cells becomes much longer and larger, and near its lower extremity contains a 

 rounded, not sharply marked-off mitochondria! body, formed of an outer zone of 

 chondriosomes and a clear central fluid, in the center of which a coarse granule may 

 be noticed. The body of Retzius is described by N. Van der Stricht in the cochlea 

 of the adult guinea pig and bat (p. 653) as formed "d'une couche compacte renfer- 

 mant generalement un ou plus rarement deux corpuscles." The significance of the 

 central granule is uncertain, but the presence of such an accumulation of chondrio- 

 somes near the nucleus, and particularly at the lower pole of the cell, where the 

 nutritive supply affects and penetrates into the cell body, seems natural and logi- 

 cal. Moreover, the inconstant occurrence of this body may be ascribed to a trans- 

 ference of its chondriomites toward the more superficial portions of the cytoplasm. 

 In other words, it seems to be a source for developing mitochondria, whence they 

 migrate into other parts of the cell. 



The " Spiralkorper " of Hensen is described by Retzius (1884, 1900) as granu- 

 lar; it has also been observed by v. Spee (1901), Held (1902), N. Van der Stricht 

 (1908), and Kolmer (1909). V. Spee regards this body as a transformed "central 

 corpuscle" surrounded by pigment granules. N. Van der Stricht considers it as a 

 "centrosome" derived from an accessory central corpuscle of the attraction sphere, 

 this corpuscle becoming shifted from the surface into the depth of the cell. The 

 body of Hensen is not apparent in the earliest stages of development (fig. 1), but 

 makes its appearance later in some of the outer acoustic elements beneath the free 

 apex of the cell (fig. 20, oh 1 , oh 11 , oh m ; fig. 19, oh 11 ). Like the body of Retzius, it 

 is not a constant, permanent structure. It is essentially mitochondria! in nature, 

 being formed of densely accumulated and packed chondriomites (fig. 20), and some- 

 times contains a kind of centrosome, a clear central area surrounding a special 

 granule. This mitochondria! body should not be confounded with the long axial 

 cone composed of closely arranged chondriomites or chondrioconts, which is often 

 visible between the apex and nucleus of the cell. The base of this cone contains the 

 body of Hensen and is applied against the free surface of the cell. 



