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



primitive nerve fibrils,* I am unable to determine. I limit 

 myself here to the simple facts, so far as I can represent them. 

 I shall again have occasion to refer to the significance of the 

 spiral-fibre system. 



COCHLEA OF BIRDS AND AMPHIBIA. 



The cochlea of Birds presents a simple structure when com- 

 pared with that of Mammals. In it we find a membrana basi- 

 laris extended between two cartilaginous rods, whilst the roof 

 of the ductus cochlearis is formed by the already described 

 tegmentum vasculosum. The lining of the ductus is composed 

 of epithelial cells of various size and form ; of hair cells, and 

 granule cells ; the two latter forms, however, being only 

 present at the points where nerves pass through the wall 

 of the cochlea ; and of a membrana tectoria. 



The large epithelial cells are very clear and transparent, and 

 of columnar form, attaining their greatest length upon the so- 

 called auditory teeth, which are processes of the inferior quad- 

 rangular cartilaginous rod. Hasse calls them " tooth-cells " 

 (Zahn-zellen) ; they probably, he thinks, secrete the membrana 

 tectoria. This last is expanded over the whole region of the hair 

 cells, but is never adherent. In the lagena it assumes the cha- 

 racters of a mucous membrane, with numerous otoliths in its 

 interior. Its tympanal surface exhibits a regular mosaic, from 

 the impressions of the hair cells, the cilia of which project into 

 the substance of the membrane. The hair cells themselves, as 

 in Mammals, occupy only a definite zone in the body of the 

 cochlea. The blind end of the lagena is, however, completely 

 filled with them. 



Each hair cell is surrounded by a circle or crown of clear 

 columnar epithelial cells the tooth cells of Hasse; it is of 



* Max Schultze. According to a written communication, of which, 

 owing to the kindness of the author, I can take advantage, this observer 

 rests his statements respecting the direct bending round of the here non- 

 medullated auditory fibres into the spiral fibrous bands essentially upon 

 a series of specimens prepared from the human subject. He compares 

 this spirally running layer of non-medullated nerve fibres with the optic 

 fibre layer of the retina, into which the medullated optic fibres similarly 

 and immediately curve round. 



