The horse is, to a certain extent, also an illustration of this. He requires an extended field of vision to warn him of the approach of his enemies in his wild state, and a direction of the orbits somewhat forward to enable him to pursue with safety the headlong course to which we sometimes urge him; and for this purpose his eyes are placed more forward than those of cattle, sheep, or swine. That which Mr. Percivall states of the horse is true of our other domesticated animals:
"The eyeball is placed within the anterior or more capacious part of the orbit, nearer to the frontal than to the temporal side, with a degree of prominence peculiar to the individual, and, within certain limits, variable at his will."
In many of the carnivorous animals the orbit encroaches on the bones of the face. A singular effect is also produced on the countenance, both when the animal is growling over his prey and when he is devouring it. The temporal muscle is violently acted upon; it presses upon the cartilage that forms part of the external ridge; that again forces itself upon and protrudes the eye, and hence the peculiar ferocity of expression which is observed at that time. The victims of these carnivorous animals are also somewhat provided against danger by the acuteness of sight with which they are gifted. Adipose matter also exists in a considerable quantity in the orbit of the eye, which enables it to revolve by the slightest contraction of the muscles.
We should scarcely expect to meet with cases of fracture of the orbital arch in the dog, because, in that animal, cartilage, or a cartilago-ligamentous substance, occupies a very considerable part of that arch; but I have again and again, among the cruelties that are practised on the inferior creation, seen the cartilage partly, or even entirely, torn asunder. I have never been able satisfactorily to ascertain the existence of this during life; but I have found it on those whom I have recommended to be destroyed on account of the brutal usage which they had experienced. Blows somewhat higher, or on the thick temporal muscle of this animal, will very rarely produce a fracture.
A
cases of disease in the eye may be interesting and useful.
Case
I. — The eyes of a favourite spaniel were found inflamed and impatient of light. Nothing wrong had been perceived on the preceding day. No ulceration could be observed on the cornea, and there was but a slight mucous discharge. An infusion of digitalis, with twenty times the quantity of tepid water, was employed as a collyrium, and an aloetic ball administered. On the following day the eyes were more inflamed, The collyrium and the aloes were employed as before, and a seton inserted in the poll.
Three or four days afterwards the redness was much diminished, the discharge from the eye considerably lessened, and the dog was sent home. The seton, however, was continued, with an aloetic ball on every third or fourth day.