280 HEAD AND NECK 



If the stuffing in the mouth has not been previously removed, it should 

 be taken out now. When this has been done, divide the external maxillary 

 artery and the anterior facial vein at the point where they cross the lower 

 border of the mandible. Next detach the anterior belly of the digastric from 

 its attachment to the anterior part of the medial aspect of the lower border 

 of the mandible ; and then, with the saw, cut through the mandible lateral 

 to the median plane. 1 It is essential that the division of the anterior part 

 of the mandible should be slightly lateral to the median plane on each 

 side, in order that the median part of the bone, with the attachments 

 of the genioid muscles, may be left intact. 



After the division of the bone has been completed the lower border of 

 the lateral part of the mandible must be everted, turned slightly upwards, 

 and fixed in position with hooks. When this has been done the boundaries 

 and contents of the submaxillary region can be examined. 



Part of the region has already been seen as the digastric portion of the 

 anterior triangle of the neck, but it will now be obvious that the region 

 occupied by the submaxillary gland is much more extensive than the 

 digastric triangle ; for, although both are bounded anteriorly and posteriorly 

 by the anterior and posterior bellies of the digastric muscle, the upper 

 boundary of the digastric triangle is the lower border of the mandible, 

 whilst the submaxillary region extends upwards to the level of the mylo- 

 hyoid ridge on the inner surface of the mandible. 



After the mandible has been turned upwards the dissector should 

 proceed, in the first place, to examine the relations of the digastric and 

 stylo-hyoid muscles, then the mylo-hyoid muscle, and afterwards he must 

 study the submaxillary and sublingual glands and the deeper structures 

 which are found in the medial boundary of the submaxillary region. 



Musculus Digastricus. This muscle limits the sub- 

 maxillary region inferiorly and separates it from the carotid 

 and submental triangles. 



The anterior belly of the digastric springs from the inner 

 surface of the lower border of the mandible close to the 

 symphysis ; and the posterior belly arises from the mastoid 

 notch of the temporal bone/)n the medial side of the mastoid 

 process. ^Thie~tw^^eTIies~converge upon the upper border of 

 the hyoid bone, where they are united by an intermediate 

 tendon, which is attached to the hyoid bone at the junction 

 of the body with the great cornu, by a strong loop of fibrous 

 tissue developed from the deep cervical fascia. Posterior to 

 the loop, through which it plays, the intermediate tendon 

 passes through the cleft lower end of the stylo-hyoid muscle. 



Relations. The anterior belly is covered by the skin, 

 superficial fascia and the platysma, and the deep fascia. It 

 is overlapped by the anterior border of the submaxillary gland, 

 and its deep surface is in contact with the mylo-hyoid muscle. 

 Its anterior border is the posterior boundary of the submental 



1 If the part is soft and pliable there may be no necessity to make this 

 division of the bone. 



