CHAP, iv.] 



HEARING. 



1345 



or faintly fibrillated ground substance, traversed by blood vessels, 

 but free from nuclei. Lower down scattered nuclei or rather 

 connective tissue corpuscles make their appearance, but the 

 ground substance in which they lie remains for the most part 

 hyaline, the tissue having an aspect not unlike that of cartilage. 

 Still lower down the groundwork is broken up, in the ordinary way, 

 into bundles of connective tissue. The branchlet of the auditory 

 nerve, reaching the ridge at its base, not far from its middle, 

 spreads out fanwise into nerve-fibres and bundles of nerve-fibres, 

 which in a more or less plexiform manner run vertically upwards 

 towards the summit of the ridge along its whole length. Hence 

 in a transverse section of the ridge the nerve-fibres are seen 

 ascending, in a vertical direction, through the connective tissue 

 cushion to the epithelial cap, in which they are lost to view. So 

 long as it remains in the connective tissue cushion each fibre re- 

 tains all its constituents, neurilemma, medulla, and axis cylinder ; 

 upon entering the epithelium it loses as we shall see its neurilemma, 

 and in most instances its medulla. 



In a vertical section of a ridge, the thickened epithelium 

 forming a cap to the ridge is seen to have special characters 



ah 



--co 





FIG. 178. DIAGRAM TO ILLUSTRATE THE STRUCTURE OF A CRISTA OR A MACULA. 



A. a portion of a crista seen under a low power, shewing c.c. the cylinder cells, 



with a. It. auditory hairs, and n. I. the nuclear layer, the nuclei being diagram - 

 matically shewn as if imbedded in a uniform ground substance, ct. the 

 connective tissue corpuscles of the derrnis with b.v. a blood vessel, and n.f. 

 nerve fibre, the latter being shewn entering into the epithelium as a simple 

 axis cylinder. 



B. cylinder and rod cells. 1, an isolated cylinder cell. 2, the same surrounded 



with a nest of nerve-fibrillse proceeding from a nerve-fibre. 3, 4, 5, various 

 forms of rod-cells. 



