THE HEAD AND NECK 299 



by a branch from this artery to the gland and by a corre- 

 sponding tributary of the anterior facial vein. 



(b) The angle of the mandible is covered by two muscles of 

 mastication, the masseter lying on the lateral surface, and 

 the pterygoideus internus on the medial surface, the latter 

 being overlapped ventrally by a part of the former. 



(c) The digastricus. Only its insertion portion is visible (the 

 origin being by a long, round tendon from the stylohyoid 

 ligament, and so from the jugular process of the occipital bone 



mh \ 



pp 



sm 



aem 



Sgl 



Fig. 108. Medial and somewhat ventral view of the muscles of the right half of the lower 

 jaw. aem, external mandibular artery; d. digastricus muscle; Ic, longus capitis muscle; Is, 

 levator scapulae major (with basioclavicularis) muscle ; mh, mylohyoid muscle (right half) ; . 

 mm, medial insertion-portion of masseter muscle; pa, parotid gland; pi, pter\-goideus 

 internus muscle; pj, jugular process; pp. pterygoid process; rca, rectus capitis anterior 

 muscle; sd. duct of submaxillary gland; sg, styloglossus and stylohyoideus minor muscles; 

 sgl, submaxillary gland (displaced ventrad) ; sm, mandibular symphysis; smj, stylohyoideus 

 major muscle. 



— Fig. 108). It passes forward along the medial surface of 

 the mandible, on the anterior ventral portion of which surface 

 it is inserted. In man and some lower primates, a second 

 fleshy portion occupies the position of the posterior part of 

 the tendon of origin, w^hence the muscle derives its name. 



(d) The mylohyoideus is a transverse sheet of muscle arising 

 from the medial surface of the mandible on either side and 

 inserted on the hyoid bone. 



(e) The sternomastoideus. Origin: In common with that of 



