THE EYE. 405 



cells are granular, possess rounded oval nuclei, and are fixed by a 

 fine, narrow process (Fig-. 252 hz), thoug-li they usually seem to be 

 rounded off without possessing- a process. 



/3. The sustentacular cells. Under the hair-cells is a finely 

 g-ranular substance, possessing- numerous romided oval nuclei, which 

 are placed in superimposed rows (Fig-. 1^1 fz), the deepest row 

 being- placed close together and immediately on the membranous 

 wall. After proper treatment and isolation these nuclei are seen to 

 belong- to narrow, elongated cells, which rest by a slig-htly widened 

 base on the wall, and are continued upwards between the hair-cells 

 to reach the surface of the epithelium, where their upper processes 

 are ag-ain slig-htly widened. 



y. The nerve-fibres (Fig-. 252 n) lose their medullary coats, ascend 

 towards the epithelium, and frequently divide to form two unequal 

 branches, which ascend to the level of the hair-cells, and curve so as 

 to com-se horizontally as extremely fine varicose fibrillae ; these fre- 

 quently form a network, of which the exact method of termination 

 has not been made out. In some cases a fine fibril may be traced 

 to the base of a hair-cell, but a direct continuation of the one into 

 the other has not yet been traced. 



VI. THE EYE. 



(Re-written by the translator,) 



The org-an of sight, the eyeball {lulbus oculi), together with its 

 appendages [tutamina ocnli), will be described in this chapter. 



A. The Eye is flattened on the outer surface, more convex on the 

 imier or deeper surface. Its principal axis is directed from behind, 

 forwards and outwards. 



The outer transparent portion of the eyeball is the cornea, which 

 forms the outer boundary of the anterior chamber. The larger, white, 

 opaque, and inner portion is the sclerotic coat, which, tog-ether with 

 two deeper tunics, the choroid coat and the retina, enclose the posterior 

 chamber of the eye. The pigmented ring placed behind the cornea 

 is the iris, and the aperture it encloses the pupil. The lens is placed 

 immediately behind the iris. On the inner side the optic nerve 

 pierces the sclerotic to enter the eyeball. 



a. The sclerotic coat [sclerotica s. sclera) forms about three- 



