THE EYE AND VISION 



215 



Coats . 



THE EYE 



(cotttinued) 



Lens . 



Chambers 



Optics . 



r Outer 



^^H T o U p g a h q 



Transparent. 



Cornea 



fibrous 



, Choroid 



Middle . 



Interior 



Iris 



Ketina 



Covers the front 

 central portion 

 of the eye. 



Contains black 

 pigment. 



Terminates 



m 



front by the 

 ciliary processes. 

 A circular perfor- 

 ated diaphragm. 

 Aperture called 



the pupil. 

 Pupil contracted 

 by circular mus- 

 cular fibres; and 

 Dilated by radial 

 fibres. [tures. 

 j Nervous struc- 

 1 Connective tissue. 

 Situated just behind the iris. 

 Double convex. Elastic. 

 Back surface more convex than the front. 

 Enclosed in a capsule. 

 Held by the suspensory ligament at its 

 circumference. [ciliary mttscle, 



Ligament relaxed by the contraction of the 

 i Between the iris and the 

 Aqueous . \ cornea. 



\ Contains a watery fluid. 

 ( Includes the greater portion 

 I of the ball. 



1 Contains a transparent jelly- 

 { like substance. 

 The eye a camera obscura or dark chamber. 

 Rays of light converge as they enter the cor- 

 Convergence increased by the lens. [nea. 

 Image (inverted) falls on the retina. 



i Cornea or lens too convex. 

 Short sight \ Remedy wear concave 

 I glasses. 



/ Cornea or lens too flat. 

 Long sight | Remedy wear convex 

 { glasses. 



f At entrance of optic nerve. 

 \ Totally insensitive to light, 

 /i of an inch outside the 

 blind spot. 



Vitreous 



Blind spot 



v Most sensitive part of the 



Retina retains impressions for about th 



of a second after its exciting cause ceases. 



