386 



MYOLOGY 





and more muscular in texture; it arises from the posterior third of the lower border 

 and from the whole of the medial surface of the zygomatic arch; its fibers pass 

 downward and forward, to be inserted into the upper half of the ramus and the 

 lateral surface of the coronoid process of the mandible. The deep portion of the 

 muscle is partly concealed, in front, by the superficial portion; behind, it is covered 

 by the parotid gland. The fibers of the two portions are continuous at their 

 insertion. 



Temporal Fascia. The temporal fascia covers the Temporalis muscle. It is a 

 strong, fibrous investment, covered, laterally, by the Auricularis anterior and supe- 

 rior, by the galea aponeurotica, and by part of the Orbicularis oculi. The super- 

 ficial temporal vessels and the auriculotemporal nerve cross it from below upward. 

 Above, it is a single layer, attached to the entire extent of the superior temporal 

 line; but below, where it is fixed to the zygomatic arch, it consists of two layers, one 

 of which is inserted into the lateral, and the other into the medial border of the 

 arch. A small quantity of fat, the orbital branch of the superficial temporal artery, 

 and a filament from the zygomatic branch of the maxillary nerve, are contained 

 between these two layers. It affords attachment by its deep surface to the super- 

 ficial fibers of the Temporalis. 



(Mandible 



1 */ 



FIG. 382. The Temporalis; the zygomatic arch and Masseter have been removed. 



The Temporalis (Temporal muscle) (Fig. 382) is a broad, radiating muscle, 

 situated at the side of the head. It arises from the whole of the temporal fossa 

 (except that portion of it which is formed by the zygomatic bone) and from the 

 deep surface of the temporal fascia. Its fibers converge as they descend, and end 

 in a tendon, which passes deep to the zygomatic arch and is inserted into the medial 

 surface, apex, and anterior border of the coronoid process, and the anterior border 

 of the ramus of the mandible nearly as far forward as the last molar tooth. 



The Pterygoideus externus (External pterygoid muscle) (Fig. 383) is a short, thick 

 muscle, somewhat conical in form, which extends almost horizontally between the 

 infratemporal fossa and the condyle of the mandible. It arises by two heads; 

 an upper from the lower part of the lateral surface of the great wing of the sphenoid 

 and from the infratemporal crest; a lower from the lateral surface of the lateral 

 pterygoid plate. Its fibers pass horizontally backward and lateralward, to be 



