TIIE OllBIT OF THE EYE. 
503 
The Horse. — It is different with the other species of animals. 
In some of them, several hours out of the four-and-twenty are 
occupied in the mastication of their food. The horse on his native 
pasture, and even domesticated and in the stable, employs a very 
considerable portion of his time in the grinding of his provender. 
There must be room for considerable development of the temporal 
muscle, in order that this may be accomplished without fatigue. 
Occasionally, and in his wild state, he needs his teeth for the pur- 
poses of offence and defence. 
The Ox.— -Nearly three-fourths of the time of the ox are em- 
ployed in the first gathering or the re-mastication of his food ; 
and ill would it fare with him, if the temporal muscle were not 
bulky and strong. We admire the mechanism by which this is 
accomplished without injury or inconvenience. The orbital sheath 
and the adeps sufficiently protect the eye from injury, while by 
their elasticity they scarcely offer the slightest impediment to the 
action of the temporal muscle on the coracoid process of the jaw. 
In the Omnivora and Carnivora. — In some of our patients, for 
purposes of offence or of defence, or the more effectual grasping 
of their prey, a sudden and violent exertion of muscular power, and 
a consequent contraction and bellying out of the temporal muscle, is 
required, and for which the imperfect socket of the orbit does not 
afford room and scope enough. There is an admirable provision for 
this in the removal of a certain portion of the orbital process of the 
frontal bone on the outer and upper part of the external ridge, and 
the substitution of elastic cartilage. This momentarily yields to 
the swelling of the muscle, and then, by its inherent elasticity, the 
external ridge of the orbit resumes its pristine form. The orbit of 
the cat, the dog, and the pig, exhibits this singular mechanism. 
The Positions of the Orbits differ in our different patients. They 
are placed at the side of the head, but the conoid cavity formed 
by the sheath of the orbit gives to all of them a prevailing di- 
rection forwards, so that, allowing for the action of the muscles 
presently to be described, the animal has a very extended field of 
vision. I cannot allow that the eye of the horse “ commands a whole 
sphere of vision but it must not be denied that his eyes are placed 
more forward than those of cattle, sheep, or swine. 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 
forwards, to enable him to pursue with safety the headlong course to 
which we sometimes urge him. 
The Position of the Orbit in the Ox. — The orbit of the eye has a 
more decidedly lateral position in the ox than in the horse, giving 
him a greater command of view on either side, but not so perfect 
in front; constituting, however, the field of vision which would 
