246 



Muscles of the Head. 



Fascia Icniporalis 



292. Fascia 

 temporalis and m. masseter, viewed from the right side. 



Fascia parotideomasseterica (see Fig. 286) covers the lateral (and medial) surface of 

 the glandula parotis as a thick nieuibrane, the in. masseter as a thinner membrane, and becomes 

 lost mrdianward 1)elow the m. zygomaticus, platysma and m. risoriiis. 



Fascia temporalis, very dense, covers the fossa temporalis externally, arises from the 

 linea temporalis .superior, divides below into two layers, separated usually by fat, and goes to 

 the medial and lateral surface of the arcus zygomaticus and the os zygomaticum. 



M. masseter. Form: Hat, (juadrangular, thick. Position: immediately upon the 

 lateral surface of tlie raums mandibulae; behind partly covered over by the glandula parotis: 

 in front and below covered by the platysma. It consists of two layers which are separated 

 fmrn one another distinctly behind only ; the external layer is the longer and broader. Origin: 

 external layer: anterior and middle part of tlie arcus zygomaticus (tendon of origin jagged, 

 reaching far downward): internal layer: middli' and posterior part of the arcus zygomaticus. In- 

 sertion: external layer: ohli(|uely backward and downward to the lateral surface of the angulus 

 mandibulae and its periphery; internal layer: downward and somewhat forward to the lateral sur- 

 face of tlif ranms mandibulae. Action : lifts the lower jaw. In ncM'vation : n. massetericus (V. 3). 



