324 ELEMENTS OF HISTOLOGY. [chap. XLI. 



this plexus are interspersed numerous nuclei. From 

 the meclullated fibres pass off minute bundles of 

 primitive fibrillse, which enter the epithelium that 

 covers the free surface of the projection. 



465. This epithelium is composed of a layer of 

 columnar or conical cells, between Avhich are wedged 

 in spindle-shaped cells ; both kinds possess an oval 

 nucleus. According to Max Schultze and others, each 

 of the spindle-shaped cells is connected by its inner 

 process with the nerve-fibrillge coming from under- 

 neath ; whereas, towards and beyond the free surface, 

 its outer process is prolonged into a long, thin, stiff, 

 auditory hair. Max Schultze, therefore, calls the 

 columnar cells epithelial; the spindle-shaped ones, 

 sensory. 



Retzius, on the other hand, maintains that, in the 

 case of fishes at any rate, the epithelial cells are those 

 which are connected each with a bundle of nerve- 

 fibrillae, and that each sends out over the internal free 

 surface a bundle of fine stiff hairs the auditory hairs. 

 The spindle-shaped cells of Max Schultze, according 

 to this theory, are only supporting cells. The free 

 surface of the epithelium is covered with a homo- 

 geneous cuticle, perforated by holes which correspond 

 to the epithelial cells and the auditory hairs. 



On the internal surface of the macula and crista 

 acustica are found the otoliths, rhombic crystalSj and 

 amorphous masses, chiefly of carbonate of lime, em- 

 bedded in a gelatinous or granular-looking basis. 



466. The cochlea (Fig. 163), as has been men- 

 tioned above, consists also of a bony shell and a 

 membranous canal, the former surrounding the latter 

 in the same way as the bony semicircular canal does 

 the membranous i.e., the latter is fixed to the outer 

 or convex side of the former. The difference between 

 the cochlea and the semicircular canals is this, that in 

 the cochlea there is a division of the perilymphatic 



