242 TWENTY-THIRD LECTURE. 



(in the latter, canals with papilla-like incurvations), as well as 



a flattened epithelium. A second watery fluid, the endo- 



lymph, fills this system of cavities. 



The otoliths are enclosed within a special saccule, and form 



columnar-shaped crystals, measuring 0.009 to 0.002 mm. 



They consist of carbonate of 

 lime, though they are said to 

 have an organic basis. 



Let us pass to the expan- 

 sion of the auditory nerve. 

 The ampullae and sacculus 

 hemi-ellipticus are supplied by 

 the vestibular branch, the sac- 

 culus rotundus, on the con- 

 trary, by a branch of the 

 cochlear nerve. It terminates 



Fig. 196. — Otoliths, consisting of carbonate .1 1 1 • . r .1 



f lime. in the duphcatures 01 the pa- 



rietes, that is at the entering 

 angle of the same, the crista acustica. 



In fishes (rays), M. Schultze, many years ago, observed 

 simple cylinder epithelium and rod cells intermingled with 

 them, reminding one of the probable terminal structures of 

 the olfactory nerves (p. 239). F. E. Schulze subsequently 

 met with a shock of uncommonly long stiff ciliae in osseous 

 fishes and tritons. The otolith sacs of fishes also presented 

 a similar condition. 



In man the salient points of the vestibular saccules are less 

 developed (maculae acusticae of Henle), but are more dif- 

 fused. Here, also, fine non-medullated nerve fibres penetrate 

 the epithelium. Two kinds of cells and cilia-like processes 

 have also been noticed. 



We now come to the cochlea. 



This convoluted structure contains two nerveless winding 

 canals, the two so-called scala of the older anatomists, the 

 scala vestibuli and the scala tympani (Fig. 197, V, T), sepa- 

 rated by an internally osseous, and externally soft membranous 

 spiral plate. Reissner has discovered, in addition, a third cen- 



