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



Hasse depicts a similar appearance in Frogs, and in the hair 

 cells of the arches of Corti in the Bird, except that here the 

 dark line extends from the cell nucleus to the free surface. 

 Hasse (1824) made the first precise observations in regard 

 to the termination of the nerves in the cochlea, by demon- 

 strating that both in Birds and Frogs the undivided non- 

 medullated nerve fibres pass directly into the basilar process 

 of the hair cells. I am able to corroborate his statements from 

 my own preparations of the cochlea of the Pigeon, where the 

 same relations are found as in the internal hair cells of Mam- 

 mals (fig. 335B). The granule cells are also present in Birds ; 

 they form a thin layer at the base of the hair cells, just 

 above the entrance of the nerves, and are likewise connected 

 with fine processes. Hasse (21, 22) regards them as mutilated 

 epithelial cells. 



My observations on the lower animals have been too few in 

 number to allow me to make any definite statements. Ac- 

 cording to Hasse (22 25), the lining of the cochlea and the 

 mode of termination of the nerves are essentially the same in 

 Frogs as in Birds ; and this, according to Leydig and Deiters, 

 apart from the insufficient evidence at present obtained in 

 regard to the mode of termination of the nerves, holds good 

 also for Reptiles. Structures corresponding to the pillars of 

 Corti, the external hair cells, and the lamina reticularis, as I 

 have already had occasion to observe, do not occur in any other 

 class, besides the Mammalia. 



COMPARATIVE ANATOMICAL AND PHYSIOLOGICAL 

 OBSERVATIONS. 



On anatomical grounds alone it is evident that the hair cells 

 constitute the essential portion of the cochlea. It must be 

 noted that the hair cells of Amphibia, Reptiles, and Birds 

 rather resemble the inner hair cells of Mammals in their 

 structure and position, in which last the introduction of the 

 arches of Corti and the outer hair cells constitutes quite new 

 features, attaining their highest expression and development 

 in Man. Just as Hasse has demonstrated in the case of Birds 

 and Batrachia, undivided axis-cylinders, forming the termi- 



