CHAPTER XIV. 
THE EYE. 
THE eye is the chief organ of sight. It is situated in the 
orbital fossa, mentioned in the chapter on the tx)nes of 
the head. It is chiefly made up of several coats around 
the outside, and in the centre by the humours of the 
eye. On the inner side of these coats is a thin membrari** called 
the retina, which contains the branches of the optic nervt. This 
receives the reflections of objects as they pass through the 
humours of the eye and from which the sensation passes 
along the optic nerve to the brain. The oblong opening seen 
in the middle of the eye is known as the pupil. If a horse be 
led from a dark stable into the light and the pupils of the 
eyes watched closely, it will be noticed that they get 
smaller; but on returning it to the stable the pupils will be 
noticed to dilate or get larger, thus it is seen that the pupils 
do not always remain the same size. The chief use of the 
pupil is to gauge the sight. At the back part of the eye are 
several muscles attached from around the eye to. the bones in 
the fossa. These muscles move the eye and assist in holding 
it to its place. Around the front part are two movable cur- 
tains, one above and the other below, called the eyelids, the 
use of which is to open and close the eye, and also to protect 
it from injuries. Around the free border of the eyelids are 
what is known as the eyelashes, which keep foreign sub- 
stances from falling into the eye. Situated in the inner angle 
is what is known as the haw of the eye; this membrane also 
helps to protect it. In the corner of this angle is a small duct 
or opening, through which a fluid called the tears passes 
down into the nasal tubes, from whence it is carried down 
through the bones of the head and emptied into the under 
part of the nostril or nose. A small gland is situated on the 
upper part of the eye. This gland secretes the tears which 
lubricate the eyes. The color of the eye is generally brown, 
but in some cases it is white. It is then called a walled eye. 
