512 PHYSIOLOGY OF THE EYE OF THE HORSE. 
to seek his food, avoid danger, and render useful service to 
his master, man. 
Man needs not this peculiar adaptation of his visual organs, 
because he fears to meet no enemy, and regards all animals as in 
every way his inferior ; his eyes, therefore, are placed in front. 
In birds, the lateral situation of these organs enables them to 
see objects in every direction; but then they cannot see small 
objects with both eyes at once, and this accounts for the rapid 
motion of their heads. The eye is supported behind by muscles 
attached to different parts of the orbit, and it rests, or is embed¬ 
ded in, a quantity of adipose matter, which occasionally be¬ 
coming partially absorbed, accounts for the sunken appearance 
which the eye sometimes presents in disease. This fatty matter 
materially assists in preserving the proper position of the eye, 
and o’ivino; steadiness to its movements. It has also another 
function to perform, of which I shall speak presently. 
In front, the eye is supported and covered by the palpebrae or 
eyelids, which, closing rapidly, protect it from any injury that 
threatens. They also, by the act of closing, afford a sufficient 
respite to a delicate organ, which would otherwise be injured and 
worn out by the constant stimulus of light. They likewise, by 
their approximation to each other, form a conduit for the tears. 
The horse is not possessed of supercilii or eyebrows, such as 
we find in the human subject, and which give peculiar expres¬ 
sion to the features; yet we find certain elevations formed by 
the orbital process of the frontal bone, also a few straggling 
hairs, and very frequently a fold of the upper lid; all of which 
combined tend to preserve the eye from the too vivid rays of 
light, and protect it from foreign bodies by which it would 
otherwise be injured. The fold of the upper lid, however, horse¬ 
men do not like to see, as they think it denotes old age, weak¬ 
ness, or disease of the eyes, which appears to me to be erroneous. 
There is much design evident in the formation and arrangement 
of the eyelashes—long and thick—different rows of them on the 
upper lid, from which direction most danger is to be feared ; thin 
towards the inner canthus, on which, during the act of grazing, 
little light can impinge ; longer and thicker towards the tempo¬ 
ral angle, where, during the bending of the head, the insect 
might be most likely to attack, and the light would fall most 
annoyingly; shorter and thinner on the lower lid, where danger 
could hardly come; but thickest there towards the nasal 
angle : and immediately below, and almost on the cheek, several 
long, scattered, half bristly hairs, projecting downwards, and 
which, while the animal gathers his food, act as watchful senti¬ 
nels, and prompt the lids to close before harm can arise, either 
