132 SPECIAL ANATOMY. 



F. Muscles of the Lower Jaw,' of mastication, 

 mansores s. manducatores. 



174. 1. Masseter, masticating muscle; external and internal 



portion. 



Pos. : before and upon the ramus maxill. infer., between arcus 

 zygomat. and angulus maxill.; above, covered by zygomatic 

 major; behind, by the Parotis. Close to its anterior border be- 

 low : art. maxillar. extern. Or. : the inferior border of the zygoma. 

 Ins.: angle a-nd external surface of ram. maxill. infer. Act.: 

 draws the lower jaw (very strongly) upwards. 



175. 2. Temporalis (s. crotaphites), temporal muscle. 



Pos.: fills up the temporal fossa; covers in. pterygoid. extern., 

 buccinator (somewhat), art. maxillar. intern, and vasa temporall. 

 proff. Or.: linea semicircularis and the walls of the temporal 

 fossa. Ins.: process, cor onoid. of the lower jaw. Act.: draws 

 the lower jaw upwards, and the condyl. maxill. backwards into 

 the articular fossa. 



176. 3. Pterygoideus internus (s. major] thick, four-sided, 



(masseter internus). 



Pos.: in the fossa zygomat., along the inner surface of the 

 ramus maxill. infer., separated from it by nn. dental., lingual., 

 art. and ven. dental, infer., and lig. laterale intern. External to 

 m. circumflex, palati, gland, submaxillar. and pharynx. Or.: 

 fossa pterygoidea. Ins.: angulus maxillas (internal surfaces). 

 Act.: draws the lower jaw strongly upwards, as well as rather in- 

 wards. 



177. 4. Pterygoideus externus (s. minor), short and thick. 



Pos. : horizontal between ala externa proc. pteryg. and collum 

 maxill. infer.; on the outer side of pter ygoid. intern., inside of 

 ram. maxill. and m. temporalis. Or. : by two heads (which fre- 

 quently embrace art. maxill. intern.) ; a. from the external surface 

 of ala extern, proc. pterygoid. and proc. pyramid, oss. palati. b. 

 from the crista and spina alse magnx of the sphenoid bone, be- 

 tween fossa temporal, and zygomatica. Ins.: the depression 

 before the col/um condyli maxill., and the circumference of the 

 interarticular cartilage. Act.: draws the lower jaw forwards and 

 pushes it to the other side; both acting together draw it directly 

 forwards. 



Nerves: (for one to four) ramus 3 trigemini. 



