Indeed, in the dog and the cat the zygomatic arch, strongly convex, springs up in a marked manner from the plane of the lateral aspects of the skull.
In the horse the same arch, less prominent externally, is prolonged by a rectilinear crest on the superior maxillary bone, where it is continued in forming the zygomatic or maxillary spine.
In the ox the same crest ascends a good way towards the inferior margin of the orbit in a curved direction with the concavity inferior, to redescend afterwards on the external surface of the superior maxilla.
The masseter is an elevator of the lower jaw. It acts, above all, as in the human species, in the process of mastication.
Temporal Muscle ([Fig. 89], 3).—The development of the temporal is in proportion to the energy of the movements of elevation which the lower jaw has to execute.
It arises from the temporal fossa, and is inserted into the coronoid process of the inferior maxilla.
Its development, enormous in the carnivora, is such that the muscle projects beyond its fossa. It is less voluminous in the horse, and still less so in the ox. In the latter, indeed, the temporal fossa, although deep, is of small extent (see [Fig. 62], p. 119); the frontal bone being large, it is found to be thrown back on the lateral walls of the cranium, below the osseous processes which support the horns and overhang the fossa in question, as well as the muscle which it contains.
It is covered by the auricular muscles, and by the base of the pinna of the ear.
Like the masseter, the temporal is an elevator of the lower jaw.