AND THE CRISTA SPIRALIS OF THE COCHLEA. 63 



by other agents, show the presence of innumerable mitochondria and chondrio- 

 mites throughout the cytoplasm of the sensorial cells. Near the free surface of 

 these elements the mitochondria increase in number and are in very close con- 

 tact; on the surface they form a plate which is more or less homogeneous, as 

 if the granules were fused together. In successful thin preparations the mito- 

 chondrial nature and the granular structure of the superficial plate may be observed. 

 This proves that cuticular formations belonging to the first series mentioned above 

 may be of mitochondrial origin, but in addition it is a striking proof of the mito- 

 chondria! nature of the acoustic hairs formed by this plate. F. Spec (1901), 

 Held (1902), and N. Van der Stricht (1908) have described the central corpuscles 

 of the hair-cells, and the last two authors are agreed that these diplosomes do not 

 take part in the formation either of the cuticular plate or the hairs. According 

 to N. Van der Stricht, the superficial central corpuscle of the hair-cells (crista and 

 macula acustica) forms a flagellum; Held (1909) observes two flagella for each 

 diplosome within all the epithelial cells lining the cochlear duct. The superficial 

 central corpuscle shows a flagellum prominent on the surface and on the deep face 

 a flagellum directed into the protoplasm towards the nucleus. 



The diplosomes within the irregular polygons of the sustentacular fields of the 

 organ of Corti are repelled into the enlarged axial or inner portion of the inner 

 supporting cells (fig. 4), into the enlarged lateral portion of the phalanges of the 

 outer pillars as observed by N. Van der Stricht and Held. In the phalanges of 

 the first and second rows of Deiters cells (and of the third in case of an additional 

 fourth row) in the new-born dog they are divided into two central corpuscles, one 

 of which reaches the axial segment and the other the lateral segment of the field. 

 At this stage of development (figs. 4 and 5) the central corpuscles are not displaced 

 in the small polygons of the inner pillars, in the third row of Deiters cells, and in 

 the fourth when it exists. 



What is more important in elucidation of the anatomical substratum of 

 the membrana tectoria is the appearance of the terminal bars the system of lines 

 which separates all the polygons, the apices of the cells, of the superficial mosaic, 

 and closes the intercellular spaces. These bars, described for all endothelia and 

 columnar epithelia, represent a denser and superficial portion of the intercellular 

 substance, the chemical composition of which is altered, for it takes up intensively 

 various stains (such as iron hematoxylin) in the same manner as do the central cor- 

 puscles and the cuticular superficial plates of the acoustic cells. The size of the 

 terminal bars varies according to the stage of development and the region. Orig- 

 inally thin, they remain thus in the region of the cells of Hensen and of Claudius. 

 They enlarge slightly at the surface of the crista spiralis, but become much thicker 

 on the greater epithelial ridge and between the constituents of the organ of Corti. 



My preparations from pig, bat, dog, cat, and mouse enable me fully to con- 

 firm the results obtained upon bat (Vespertilio noctuln) by N. Van der Stricht, 

 who considers the membrana reticularis of the crista and macula acustica and of 

 the organ of Corti as formed exclusively by a gradual enlargement of the terminal 

 bars. In 1876, after fixation of material by silver nitrate which stained the inter- 



