CHAP, iv.] 



HEARING. 



1011 



which they are brought about ? To these questions we can at 

 present give no satisfactory answer at all. Any attempt to 

 answer them leads us at once into speculations. The rod-like 

 appendages of the hair-cells, the so-called hairs (Figs. 181, 182) 

 are too short and uniform, to permit us to suppose that they are 

 vibrating organs responding by their vibrations to the vibrations 

 of the perilymph and so bringing those vibrations to bear on the 

 substance of the hair-cells. The vibrations find their way, so to 

 speak, to the hair-cells in some other way. The membrana tec- 

 toria (Figs. 180, 181, m.t.~) has the aspect of an organ serving to 



aaud 



FIG. 181. DIAGRAM OP THE ORGAN OF CORTI. (After Ketzius.) 



i.r. inner rod of Corti, o.r. outer rod of Corti. 



i.h.c. inner hair-cells, n.c. the group of nuclei beneath it. o.h.c. outer hair- 

 cell, or cell of Corti, of the first row, c.D. its twin cell of Deiters ; four rows of 

 these twin cells are shewn. 



n.aud. the auditory nerve perforating the tympanic lip Z., and lost to view 

 among the nuclei "beneath the inner hair-cell. Lsp.n. the inner spiral strand of 

 nerve-fibrillse. t.sp.n. the spiral strand of the tunnel, o.sp.n. 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 shewn. Nerve-fibrillse are 

 shewn stretching radially across the tunnel. 



H.c. Hensen's cells, Cl.c. Claudius cells, m.b. basilar membrane, tl. lym- 

 phatic epithelioid lining of the basilar membrane, on the side towards the scala 

 tympani. Ig.sp. spiral ligament, c'. cells lining the spiral groove, overhung by 

 l.v. the vestibular lip. m.t. the tectorial membrane ; a fragment of it is seen 

 torn from the rest and adherent to the organ of Corti just outside the outermost 

 row of outer hair-cells. 



' damp ' the vibrations of the basilar membrane, and the hairs of 

 the hair-cells may perhaps rather serve the purpose of bringing 

 their damping^action tojbear directly on the substance of the 

 hair-cells ; for the membrane in question comes down into direct 

 contact with them. We may further suppose that in the de- 

 velopment of auditory impulses, the peculiar rods of Corti (Fig. 

 182) play some special part. But concerning all these matters 

 we can at present do hardly more than make guesses, and those 

 unprofitable ones. 



Of THB 



