Prof. A. M. Mayer's Researches in Acoustics. 449 



adopt the latter view, then every thing works to produce the 

 maximum effect on the covibrating parts of the organ of Corti ; 

 for when the stapes moves inward, the pressure is thrown on the 

 outer border of the upper wall or roof of the ductus, thence 

 across to the peripheral portion of tl^e basilar membrane. This 

 action, we may say, takes place simultaneously throughout the 

 whole length of the ductus, moves downward the floor of the 

 basilar membrane, and thus presses the fluid of the scala tym- 

 pani against the fenestra rotunda and moves this membrane out- 

 ward. When, however, the stapes moves outward, the pressure 

 is relieved from the elastic basilar membrane, which is now moved 

 upward, while the fenestra rotunda moves inward*. 



There are also other anatomical facts, besides the inclination 

 of the membrana Reissneri to the plane of the membrana basi- 

 lars, and the inclination of both these membranes to the plane 

 perpendicular to the axis of the cochlea, which favour an opinion 

 that the outer or peripheral part of the basilar membrane re- 

 ceives the main part of the vibrations which enter the ductus. 

 The auditory nerve-fibrils are not attached to the Corti rods or 

 pillars, as was formerly imagined ; and therefore these bodies 

 cannot be the covibrating parts of the ductus; but the Corti 

 pillars appear to act, in conjunction with the cylindrical nerve- 

 cells of Hensen, as supports for the lamina reticularis, between 

 which and the basilar membrane are steadily and tensely 

 stretched the hair- cell cords (as I will term them) ; and to these 

 cords are attached "the nerve- fibrils. Waldeyer says on this 

 point that " The outer radial fibres direct their course, as Gott- 

 stein has found, toward the tunnel of Corti, passing between the 

 inner pillars and traversing the tunnel about midway between 

 the summit and base of the arch; in a profile view these fibres 

 appear like stretched harp-strings. On leaving the arched space 

 they pass between the outer pillars and direct their course 

 (rising a little toward the scala vestibuli) straight to the hair- 

 cells, with which they become completely fused. In several 

 preparations from the dog and the bat I have seen this ter- 

 mination of the nerves in the most convincing manner, at least 

 so far as the innermost row of hair-cells is concerned ; as to the 

 other rows, we may pretty confidently assert that the termina- 

 tion of the nerves is the same ; for we can frequently see several 

 fibres passing at the same time between the outer pillars." The 

 very fact that the number of these hair-cell cords increases 

 with the higher development of the ear shows their important 



* If we could examine at the same time vibrating points on the stapes 

 and on the fenestra rotunda with a vibration-microscope, I imagine that 

 these points would exhibit no difference in phase when the membrana 

 tympani vibrated to a note below the treble. 



Phil. Mag. S. 4. Vol. 48. No. 320. Dec. 1874. 2 G 



