of the Cochlea in Man and other Mammals. 153 



Its superior surface is rectangular, but longer than it is broad, as is 

 well seen when looking from above, in flat preparations. Externally 

 it is prolonged into a process which overlaps the superior extremity 

 of the outer rod, and terminates somewhat abruptly. The form of 

 this process will be better understood by looking at Fig. I. Below 

 it is continuous with the shaft ; the lateral surfaces are somewhat 

 quadrilateral in form, with the anterior and posterior edges concave. 

 These surfaces are divided obliquely by a curved ridge ; the upper 

 and inner is smaller, raised and marked by curved lines — the exter- 

 nal and lower division is smooth and more transparent. The inner 

 surface is concave from above downwards, and is continuous with the 

 lateral surfaces. 



The external surface is deeply concave, and receives the head of 

 the outer rod very much in the same manner as the glenoid cavity 

 receives the head of the humerus. The upper lip of this concavity 

 is continuous with the process mentioned above, the lower one is 

 rounded, and forms a sort of tubercle. 



The outer rods are attached to about the middle of the mem- 

 brana basilaris by a broad base, which is very similar to that of the 

 inner rods, but somewhat larger, and this also gradually tapers 

 towards the shaft. The shaft is cylindrical, and equal in diameter 

 to that of the inner row, as may be proved by carefully measuring 

 the two as seen in most of my preparations. The upper extremity 

 of these outer rods is also peculiar, but very different to that of the 

 inner. The superior surface is quadrilateral, but both broader and 

 longer than that of the corresponding extremity of the first row. 

 Below it is of course continuous with the shaft. 



The inner surface is very convex, forming a head which articu- 

 lates with the corresponding concavity of the inner rod. The outer 

 surface is slightly concave, and from the upper part a long slender 

 process extends outwards. This process lies at first under that of 

 the inner rod, but is prolonged much farther outwards ; it is rather 

 more slender in form, and has a handle-like enlargement at the 

 extremity : the whole will be better understood by referring to 

 Fig. I. The lateral surfaces are apparently smooth, but marked by 

 fine radiating lines. 



The articulation of the two rows is not movable ; there are no 

 ligaments, unless the membrana reticularis, w 7 hich is finely adherent 

 to the upper surfaces, may be regarded as such, but the articulating 

 surfaces may be seen to be glued together in some peculiar way. 



I now come to one of the most important features with regard 

 to these interesting little rods, namely, their relative length. Most 

 authors state that there is very little difference in the length of the 

 two rods ; this is quite a mistake, as I am about to prove, for not 

 only do the two sets of rods differ in this respect, but the length of 

 each varies according to its position in the cochlea. Thus, at the 



