766 



THE EYE AND VISION 



[CH. LVL 



eyeball is filled by the aqueous and vitreous humours and the 

 crystalline lens; but, also, there is suspended in the interior a 

 contractile and perforated curtain, the iris, for regulating the 

 admission of light, and behind at the junction of the sclerotic and 



FIG. 563. Horizontal preparation of cornea of frog ; showing the network of branched cornea-corpuscles. 

 The ground substance is completely colourless, x 400. (.Klein.) 



cornea is the ciliary muscle, the function of which is to adapt the eye 

 for seeing objects at various distances. 



The sclerotic coat is composed of white fibrous tissue, with some 

 elastic fibres near the inner surface, arranged in variously disposed 

 and interlacing layers. Many of the bundles of fibres cross the 



FIG. 564. Surface view of part of lamella of kitten's cornea, prepared first with caustic potash and then 

 with nitrate of silver. (By this method the branched cornea-corpuscles with their granular proto- 

 plasm and large oval nuclei are brought out.) x 450. (Klein and Noble Smith.) 



others almost at right angles. It is separated from the choroid by 

 a lymphatic space (perichoroidal), and this is in connection with 

 smaller spaces lined with endothelium in the sclerotic coat itself. 

 There is a lymphatic space also outside the sclerotic, separating it 

 from a loose investment of connective tissue, containing some smooth 



