DISEASES OF THE EYE. 



303 



the greater the quantity and intensity of light, the smaller 

 the central opening (pupil) in the curtain. 



The globe of the eye is set in a bony socket, moved by 

 several muscles, protected by the eyelids, eyebrows, eye- 

 lashes, and washed over with the secretion of a small gland 



-SUPERIOR RECTUS 



CHOROfD 



OPTIC NEftVP 



CHOROiO 



INFERIOR RECTUS 

 FIG. 23,-SECTioN OF HUMAN EYB, SOMEWHAT DIAGRAMMATIC (AFTER FLINT). 



(lachrymal} situated in the outer part of the socket. The 

 secretion, when it has served its purpose, is carried away 

 by the lachrymal duct into the nose. 



In the dog, a third eyelid (membrana nictitans) is pres- 

 ent at the inner corner of the eye, but is not so well devel- 

 oped as in herbivora, etc., though more; prominent in some 

 breeds, as bloodhounds. 



