234 THE ARTISTIC ANATOMY OF ANIMALS 



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. 



Cutaneous Muscles of the Head 



Occipito- Frontalis. — The epicranial aponeurosis is ex- 

 tremely thin. In the dog the occipital muscle occupies the 

 superior part of the head ; it overlies the temporal muscle. 



With regard to the frontal muscle, which is of great extent 

 in the ox (Fig. 91, F), it is represented in the horse and the 

 carnivora by a small fleshy fasciculus only, the fronto- 

 palpebral muscle, similar to the superciliary muscle. This, 

 occupying the superior and internal part of the border of 

 the orbit, ends by blending its libres with those of the 

 orbicular muscle of the eyelids at the region of the eyebrow. 



Orbicularis Palpebrarum (Fig. o, 92 ; Figs. 91, 92). — This 

 annular muscle surrounds the palpebral orifice, and takes 

 its origin on the internal part of the orbital region. In the 

 horse it arises, by a small tendon, from a tubercle which 

 occupies the external surface of the os unguis, or lachrymal 

 bone. 



