THE SPECIAL SENSES 



305 



THE EYE . 



(continued) 



Coats 



Lens 



Chambers 



Optics 



Sclerotic 



Cornea . -j 



Choroid 



Interior 



Retina 



j Tough, fibrous, 



opaque. 

 Outer . . . . -I i Transparent. 



Covers the front cen- 

 tral portion of the 

 I eye. 



f Contains black pig- 

 ment. 



1 Terminates in front 

 by the ciliary 

 processes. 

 A circular perforated 



diaphragm. 

 Aperture called the 



pupil. 



Iris . . . . \ Pupil contracted by 

 circular muscular 

 fibres ; and 

 I Dilated by radial 

 I fibres. 



j Nervous structures. 

 ' Connective tissue. 

 Situated just behind the iris. 

 Double convex. Elastic. 

 Back surface more convex than the front. 

 j Enclosed in a capsule. 



: Held by the suspensory ligament at its circum- 

 ference. 



I Ligament relaxed by the contraction of the 

 I. ciliary muscle. 



j Between the iris and the cornea. 

 ' Contains a watery fluid. 

 f Includes the greater portion of 

 I the ball. 



j Contains a transparent jelly-like 

 ( substance. 



The eye a camera obscura or dark chamber. 

 Rays of light converge as they enter the cornea. 

 Convergence increased by the lens. 

 Image (inverted) falls on the retina. 



j Cornea or lens too convex. 



'/ Remedy wear concave glasses. 



j Cornea or lens too flat. 



' Remedy wear convex glasses. 



j At entrance of optic nerve. 



( Totally insensitive to light. 



( IB Of an inch outside the blind 



spot. 



] Marked by a slight depression. 

 [ Most sensitive part of the retina. 

 Retina retains impressions for about i of a sec- 

 ond after its exciting cause ceases. 



f Aqueous 



I Vitreous 



Short-sight , 

 Long-sight , 

 Blind spot 



Yellow spot 



