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AN AMERICAN TEXT-BOOK OF PHYSIOLOGY. 



which are disposed along the edge of the spiral lamina in two rows, an inner 

 and an outer. The inner rods have their feet on the basilar membrane near its 

 median attachment; they lean outward and upward, and at their upper extrem- 

 ity join or articulate with the heads of the outer rods, whose feet are fastened to 

 the basilar membrane more externally. The two rows of rods are thus joined 

 together like the rafters of a house, and enclose beneath them a canal known 

 as the tunnel of the organ of Corti. The inner rods are more numerous than 

 the outer, so that the latter are fastened rather between than to the ends of the 

 former. Leaning against the inner or median side of the inner row of rods 

 is a single row of hair-cells (Fig. 281), much like those described as seated on 

 the maculae and crista? of the labyrinth, to which hair-cells filaments of the 



l.r 



n.aud l.t i.spn t.spn o.spn 



FIG. 281. Diagram of the organ of Corti (from Foster, after Retzius) : i.r, inner rod of Corti ; o.r, outer 

 rod of Corti ; i.hc, inner hair-cell ; n.c, the group of nuclei beneath it ; o.he, outer hair-cells, or cells of 

 Corti ; C.D, the twin cells of Deiters (four rows) ; n.aud, the auditory nerve perforating the tympanic lip, 

 l.t, and lost to view among the nuclei beneath the inner hair-cells ; i.spn, the inner. spiral strand of nerve- 

 fibrils ; t.spn, the spiral strand of the tunnel ; o.spn, the outer spiral strand belonging to the first row of 

 outer hair-cells ; the three succeeding spiral strands belonging to the three other rows are also shown ; 

 nerve-fibrils are shown stretching radially across the tunnel'; H.c, Hensen's cells; Cl.c, Claudius' cells; 

 t.l, lymphatic epithelioid lining on the side toward the scala tympani ; Ig.sp, ligamentum spirale ; c, cells 

 lining the spiral groove, overhung by the vestibular lip, l.v ; m.t, tectorial membrane ; a fragment, torn 

 from it, remains attached to the organ of Corti just outside the outermost row of hair-cells. 



auditory nerve are distributed. Closely applied to the single row of hair- 

 cells, on the inner side, are several rows of columnar cells gradually decreas- 

 ing in size toward the median line, and beneath the whole is a group of nuclei. 

 External to the outer row of rods, and separated from it by a space, are four 

 parallel rows of hair-cells known as the cells of Corti ; their bodies do not 

 reach downward as far as the basilar membrane, and just below each row is a 

 bundle of nerve-fibres which have traversed the tunnel of Corti and then have 

 changed their direction from a radial to a longitudinal or spiral one. These 

 fibres, and others having a more direct course, one by one end in clusters 

 encircling the individual hair-cells. 



Four rows of peculiarly-modified columnar cells, the cells of Deiters, are 

 inserted closely between the cells of Corti, the outermost row being external 

 to the fourth row of Corti. These cells rest below on the basilar membrane. 

 Still external to these groups of cells is a series of rows of tall columnar cells 

 of simple character supported upon the basilar membrane, and rapidly decreas- 

 ing in height externally into a layer of cuboidal epithelium covering the outer 

 part of the basilar membrane. The rods of Corti are peculiarly shaped at the 



