184 HAND-BOOK OF PHYSIOLOGY. 



(canalis reuniens) uniting it with the sacculus. The scala media (like the 

 rest of the membranous labyrinth) contains "endolymph." 



Organ of Corti. Upon the basilar membrane are arranged cells of 

 various shapes. 



About midway between the outer edge of the lamina spiralis and the 

 outer wall of the cochlea are situated the rods of Corti. Viewed sideways, 

 the rods of Corti are seen to consist of an external and internal pillar, 

 each rising from an expanded foot or base on the basilar membrane. 

 They slant inward toward each other, and each ends in a swelling termed 

 the head; the head of the inner pillar overlying that of the outer (Fig. 





FIG. 363. Vertical section of the organ of Corti from the dog. 1 to 2, homogeneous layer of the 

 so-called membrana basilaris; u, vestibular layer; v, tympanal layer, with nuclei and protoplasm; 

 a, prolongation of tympanal periosteum of Jamina spiralis ossea; c, thickened commencement of 

 the membrana basilaris near the point of perforation of the nerves h; d, blood-vessel, (vas spirale); 

 e, blood-vessel; /, nerves; g, the epithelium of the sulcus spiralis internus; i, internal or tufted cell, 

 with basil process fc, surrounded with nuclei and protoplasm (of the granular layer), into which the 

 nerve-fibres radiate; Z, hairs of the internal hair-cell; n, base or foot of inner pillar of organ of Corti; 

 m, head of the same uniting with the corresponding part of an external pillar, whose under half is 

 missing, while the next pillar beyond, o, presents both middle portion and base; r,*,d, three external 

 hair-cells; , bases of two neighboring hair or tufted cells; x, so-called supporting cell of Hensen; w, 

 nerve fibre terminating in the first of the external hair-cells; II to I, lamina reticularis. X 800. 

 (Waldeyer.) 



363). Each pair of pillars forms, as it were, a pointed roof arching over 

 a space, and by a succession of them, a little tunnel is formed. 



It has been estimated that there are about 3000 of these pairs of pillars, 

 in proceeding from the base of the cochlea toward its apex. They are 

 found progressively to increase in length, and become more oblique; in 

 other words, the tunnel becomes wider, but diminishes in height as we 

 approach- the apex of the cochlea. Leaning, as it were, against these 

 external and internal pillars are certain other cells, of which the external 

 ones terminate in small hair-like processes. Most of the above details 

 are shown in the accompanying figure (Fig. 363). This complicated 

 structure rests, as we have seen, upon the basilar membrane; it is roofed 

 in by a remarkable fenestrated membrane (lamina reticularis of Kolliker), 

 into the fenestrae of which the tops of the various rods and cells are re- 

 ceived. When viewed from above, the organ of Corti shows a remarkable 



