THE TRIGEMINAL MUSCLES. 



475 



and fading out anteriorly beneath the facial muscles. Posteriorly it becomes thicker 

 and divides into two layers to enclose the parotid gland {^parotid fascia^, the super- 

 ficial layer becoming continuous behind with the layer of the deep cervical fascia 

 which encloses the sterno-mastoid muscle, while the deeper layer is connected inter- 

 nally with the styloid process and joins the deep cervical fascia below. A thickening 

 of this deeper layer forms a fiat band, the stylo-mandibidar ligameiit, which passes 

 downward and outward from the styloid process to the angle of the jaw. 



2. Temporalis (Fig. 495). 



The temporal fascia forms a strong aponeurotic membrane attached above to the 



superior terrrj^oral line and the portion of bone between this and the inferior line, 



 being along this attachment continuous with the periosteum. Below it divides into 



two layers which are separated by a quantity of adipose tissue, through which the 



Fig. 495. 



Temporal 

 fascia (cut) 



Temporal — r^ 

 muscle, \ 



partially \*%* 



exposed 



Buccinator 



Masseter, 

 deep portion 



Masseter, superficial portion 



Orbicularis 

 oris 



Lateral aspect of skull with temporal, masseter, buccinator, and oral muscles in place. 



middle temporal artery may run, and is attached to the zygoma, its superficial layer 

 inserting into the upper border of the arch and its deeper layer into the inner surface. 



Attachments. — The temporal muscle arises from the upper half of the deep 

 surface of the temporal fascia and from the whole extent of the floor of the temporal 

 fossa. Its fibres converge to an exceedingly strong tendon, which inserts into the 

 coronoid process of the mandible, occupying both its borders, the whole of its inner 

 surface, and a varying amount of its outer surface. 



Nerve-Supply. — By the anterior and posterior deep temporal branches from 

 the anterior portion of the mandibular division of the trigeminus. 



Action. — To raise the mandible. The more posterior fibres serve to retract 

 the jaw, acting thus as an antagonist of the external pterygoid. 



