CHAP, iv.] HEARING. 217 



cells of the organ of Corti may be regarded as slung from the 

 trellis work of the reticulate membrane, or perhaps more exactly 

 slung between it and the basilar membrane. The whole reticulate 

 membrane thus seeming to serve as a support to the outer hair- 

 cells, may justly be regarded as cuticular; and if so we may 

 regard the rods of Corti as cuticular also. It must however be 

 remembered that the rods are very peculiar in nature ; one might 

 be inclined to compare them on the one hand with the hyaline 

 border of a ciliated cell, and on the other hand with the outer 

 limbs of the rods and cones of the retina. 



The rods thus form along the length of the spiral of the cochlea 

 a double row, inner and outer. In each row the heads are in 

 contact, the adjoining sides being as we said flat ; the phalangar 

 processes of the outer row are also in contact with each other, side 

 by side ; and the outer heads fit into the inner heads. Hence 

 when the organ of Corti is viewed from above (Fig. 180 D) along 

 a portion of its length, this part of the organ very strikingly 

 resembles the keys of a piano. The inner rods however are more 

 numerous than the outer rods, in the proportion of 5 '6 to 3 '8, so 

 that each outer rod is not exactly opposite an inner rod, but fits 

 into more than one inner rod. 



While, in the case of both inner and outer rods the heads are 

 in contact sideways, that is to say along the length of the spiral, 

 and the same is true of the expanded feet also, the more slender 

 limbs are not in contact but leave spaces or clefts between every 

 two rods in each row. Through these clefts nerve filaments as 

 we shall see make their way from the region of the inner hair 

 cells into the spiral tunnel formed by the rows of inner and outer 

 rods on each side and by the basilar membrane at the base, and 

 beyond this, from the tunnel into the region of the outer hair-cells. 



834. The inner hair-cells form a single row to the inner 

 side of the inner rods. Each hair-cell (Fig. 180 A) bears much 

 resemblance to, and may be regarded as analogous to a cylinder 

 cell of a crista or macula. It is flask-shaped, ending below in a 

 blunt cone, and bears in its lower part a large spherical nucleus. 

 Its upper end, circular or oval in outline, has a hyaline border like 

 that of a ciliated cell, and from this project a number, a dozen 

 or more, not of long hairs but of short (5 JJL) rods, definitely 

 arranged in a gentle curve (Fig. 180 A'), lying at about the 

 middle of the free surface of the cell with the hollow of the curve 

 looking inwards towards the spiral lamina. The substance of 

 the cell is granular, but very watery and very delicate, readily 

 shrinking and becoming deformed under the influence of reagents. 



The pointed base of the inner hair-cell dips down into a group 

 of nuclei, which form, as we have said, something like the nuclear 

 layer of the crista or macula. There has been much difference 

 of opinion about these nuclei, but they appear to belong to cells 

 very like the rod cells of the crista and macula. The scanty cell 



