OUR EYES. 
125 
OUK EYES. 
ABSTRACT OF MR. W. SQUARE's PAPER. 
(Read December 8th, 1870.) 
The lecturer said that the ey.es might be treated as most of the 
other organs of the body, and described anatomically and physio- 
logically. He touched briefly upon the external structures — the 
lids, eyelashes, tears, and conjunctiva — and then went on to the 
description of each of the various structures of the eye itself. 
The sclerotic is the tough fibrous coat forming the great bulk of 
the external surface ; in front it alters its structure and is known 
as the cornea. Inside the sclerotic is the choroid — a coat composed 
of blood-vessels and pigment cells — at the junction of the cornea 
and sclerotic, and immediately behind it is placed the ciliary 
muscle, the part concerned in the accommodation of the eye. 
The iris is a moveable curtain suspended in the aqueous humour, 
and has a central aperture — the pupil. This is capable of contrac- 
tion and dilatation. The humours are three in number : the aqueous, 
vitreous, and the lens. The lens is biconvex, and is altered in 
accommodation by the action of the ciliary muscle. It is composed 
of pectinated fibres; it is contained in a capsule. The retina is 
the most complex of all the internal structures of the eye. It 
consists of eight layers. 
The lecturer described the intimate relation between its various 
parts, and especially dwelt upon the fibres of Miiller, the bacillary 
layer, and its rods and bulbs. 
The optic disc and the yellow spot were next described, and the 
optic nerves and optic tracts, the optic commissure, and the 
general anatomical connexion of the eyes and the brain. 
The anatomical division of the lecture was concluded by a 
description of the appearances seen in the eye during life by the 
aid of the ophthalmoscope. 
The physiological part of the lecture commenced by a brief 
description of the uses of the external parts. For optical purposes 
rays of light must be supposed to come from every object that the 
eye becomes cognizant of. The behaviour of rays of light during 
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