170 THE AUDITORY NERVE AND COCHLEA, BY W. WALDEYER. 



appearing in the form of nucleated enlargements of the axis- 

 cylinder. (See fig. 26, B, p.. 173, vol. i.) 



Proceeding onwards from the ganglion, the fibres, which are 

 still always strongly medullated, form a flat plexiform expan- 

 sion (the anastomoses and communications being very frequent) 

 (fig. 330), which lies between the tympanal and vestibular 

 lamina of the lamina spiralis ossea, though much nearer to the 

 former. The anastomoses between the coarser and finer fas- 

 ciculi may here be distinguished. The latter (fig. 330, 6) are 

 very numerous in Man, just before the entrance of the nerves 



Fig. 330. Lamina spiralis in the first turn of the cochlea, seen 

 from the tympanal surface, from a child aged one year and a half, 

 showing the expansion of the nervus cochlearis. a, Large trunk, 

 with numerous anastomoses ; 6, zone-like terminal series of fine 

 anastomoses ; c, membrana basilaris. Magnified 30 diameters. 



into the ductus cochlearis, so that in consequence a delicate 

 dentated line appears in surface views.' The several terminal 

 fasciculi of the nerves quickly become attenuated, whilst the 

 fibres lose the greatest part of their medullary sheaths, and 

 pass through fine canals of the membrana basilaris into the 

 cavity of the ductus cochlearis. 



The minute and in general circular canals for the nerves are of 

 measurable length in the upper turn of the cochlea, since they traverse 

 the membrana basilaris obliquely ; and even anastomoses are observa- 

 ble between the several pale nerve fibres during their passage. In 

 the lower turn, on the other hand, their course is more vertical. In 

 surface views the holes are seen to be, in Man, small, round, and in 

 close proximity; but they are larger, and of elliptic form, in the Dog" 



