46 ANATOMY OP THEIIEAD AND NECK. 



SUBMAXILLARY REGION. 



The dissection of the carotid artery will have exposed 

 and prepared a number of parts situated below the in- 

 ferior maxillary bone and between it and the hyoid bone. 



The DIGASTRICUS MUSCLE, lying above the hyoid bone and 

 connected with it, is composed of two rounded bellies con- 

 nected by a central tendon, the central tendon being the 

 part attached to the hyoid bone ; these two bellies form an 

 obtuse angle with each other ; the posterior one arises from 

 the digastric fossa of the temporal bone and is consequently 

 covered in by the mastoid portion of the sterno-mastoid 

 muscle and by the parotid gland. The anterior belly, 

 closely connected, though not united with the correspond- 

 ing part of the same muscle on the other side of the neck, 

 arises from the side of the symphysis of the lower jaw ; 

 these two portions are attached by their central tendon to 

 the body and greater cornu of the os hyoides. The tendon 

 of the muscle is held in its place by a strong fascia and by 

 fibres of the stylo-hyoid muscle which surround it. The 

 posterior belly of this muscle crosses the carotid vessels, 

 and along its lower border will be found the occipital 

 artery and the hypoglossal nerve. The facial nerve sends 

 a branch to this muscle soon after its exit from the stylo- 

 mastoid foramen. 



The STYLO-HYOID MUSCLE is in close connection with the 

 preceding ; it arises from the styloid process of the tem- 

 poral bone, and passes down behind and to the inner side 

 of the posterior belly of the digastricus ; at its lower part 

 it splits, and allows the digastric tendon to pass through 

 its substance ; it is inserted into the os hyoides at the union 

 of its body and cornu. It is sometimes wanting. The 

 facial nerve sends a branch to this muscle also, soon after 

 it emerges from its foramen. 



The anterior belly of the digastricus is to be removed, and the sub- 

 maxillary gland freed from extraneous cellular tissue, and loosened 

 from its attachments. 



The SUBMAXILLARY GLAND is a salivary gland, next in 

 size to the parotid, which it resembles in general structure; 

 it lies above the digastricus and upon the mylo-hyoicl 

 muscle ; it is partly concealed by the lower jaw, though it 

 descends a variable distance down the neck ; it is traversed 

 by the facial artery, which distributes numerous small 



