18 
GEORGE G. VAN MATER. 
SOME VETERINARY OPHTHALMOLOGY. 
By George G. Van Mater, M.D., D.V.S., Lecturer on Ophthalmology to the 
American Veterinary College. 
In Act III. of “Romeo and Juliet” we find, “ Men’s eyes 
were made to look, and let them gaze,” and having been re¬ 
quested to present some ophthalmological points in a veter¬ 
inary light, I thought the above quotation pat, and so pre¬ 
faced this paper with it. The eyes themselves do not see. 
Shakespeare again, in “Julius Caesar,” says: “ The eye sees 
not itself, but by reflection, by some other things.” Through 
the medium of an eye external impressions are focused upon 
the retina, which retina is an expansion of the optic nerve. 
Said optic nerve (the second pair) transmits the message to 
the perceptive organism, and thus we see. Thus, as in many 
another instance, we see the Queen’s English misrepresent¬ 
ing facts, for when we say, the eye “ sees,” we are in error, 
for the eye does not see. 
There has been much and weighty discussion on the ori¬ 
gin of the optic nerve. We will briefly say that this nerve 
is continued externally with the side of the thalamus opticus, 
forming the corpora geniculata. By some the thalamus op¬ 
ticus is believed to be the true origin. Others, that as the 
external corpora geniculata is in contact with the natis, and 
the testis in contact with the internal corpora geniculata by 
a band of white fibres, therefore the corpora quadrigemina 
furnishes the source of origin. In mammals the ocular ap¬ 
paratus takes similar form to the human, with the exception 
that in some cases it may be elongated somewhat. In mam¬ 
mals the eyes are obliquely set. Only in man, apes and some 
night birds are the eyes so set as to permit visual lines di¬ 
rectly ahead in parallels. The eye of the horse measures 
transversely 1.417 inches and vertically 1.575 inches. The 
eyeball, or bulbus, is protected anteriorly by two movable 
folds—the lids—superior and inferior, having an inner and 
outer angle, which angles are called the internal and external 
canthus. On the edge of each lid, very near the internal 
