MYOLOGY 



233 



Its posterior border is in relation with the parotid gland 

 (Fig. 90, 14 ; Figs. 91, 92), this gland being situated between 

 the corresponding border of the lower jaw bone and 

 the transverse process of the atlas. Such are the general 

 characters ; the following are the particular ones : 



In the carnivora it is thick and convex. In the horse it 

 is flat, but more expanded ; it forms the flat of the cheek. 

 In the ox it is flat, as in the latter ; but, while being less 

 thick, it is more prolonged in the vertical direction. 



The form of the osseous parts which give it origin is, 

 besides, in relation with these differences, and explains the 

 peculiar characters which the masseter presents. 



Fig. 89. — Myology of the Dog : Masticatory Muscles (a Deeper 

 Dissection than that shown in Fig. 90). 



I, Zygomatic arch ; 2, masseter ; 3, temporal exposed by the suppres- 

 sion of the auricular and occipital muscles and the pinna of the ear ; 4, 

 auditory canal ; 5, inferior maxillary bone ; 6, digastric. 



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 

 maxiUary spine. 



In the ox the same crest ascends a good way towards the 

 inferior margin of the orbit in a curved direction with the 



