DISSECTION OF THE HEAD AND NECK. 171 



the submaxillary salivary gland lies internal to it. In passing obliquely 

 backwards and downwards, it rests on the internal pterygoid muscle, and 

 is partly covered by the lymphatic glands, under cover of which it de- 

 taches its submental branch. It then comes into company with the vein 

 of the same name, and with Stenson's duct ; and the three vessels turn 

 round the edge of the ramus to reach the face, the artery being below, 

 the vein in the middle, and the duct superior. Where the artery turns 

 round the ramus, it is very favourably placed for taking the pulse, since 

 it is a vessel of considerable size, is in an easily accessible position, rests 

 directly on the bone, and is almost subcutaneous, only the thin panni- 

 culus intervening between it and the skin. 



The Submental Artery crosses downwards beneath the inferior belly of 

 the digastricus, then along the surface of the mylo-hyoideus, which it 

 perforates a few inches above the symphysis. It will be followed to its 

 termination in the dissection of the mouth. 



The Submaxillary Vein (Plate 27) is in contact with the artery where 

 the vessels turn round the ramus ; but as it passes backwards, it recedes 

 slightly from the artery, and follows the posterior border of the sub- 

 maxillary gland. It leaves the space above the angle of the jaw, and is 

 continued along the lower edge of the parotid to join the jugular. At the 

 lymphatic glands it receives the submental vein, a larger vessel than the 

 artery of the same name. 



Stenson's Duct (Plate 27), after crossing the sterno-maxillaris tendon, 

 passes into the space, at the posterior edge of the submaxillary salivary 

 gland. It passes downwards on the internal pterygoid muscle, placing 

 itself in contact with the submaxillary vein, in company with which and 

 the artery it turns round the bone to reach the face. It is here the most 

 superior of the three vessels ; and from its being superficially placed 

 and resting on the bone, it is liable to be opened when a blow is delivered 

 over this region. 



The DiGASTBicus. This muscle is named from its having two fleshy 

 bellies, with an intermediate tendon. The upper beUy arises from the 

 styloid process of the occipital bone, being confounded with the stylo- 

 maxillaris. It is succeeded by the intermediate tendon, which plays 

 through the tendon of the stylo-hyoid muscle ; but this and the upper 

 belly are at present concealed within the jaw. The lower belly is placed 

 in the intermaxillajy space, where it is partly covered by the lymphatic 

 glands, and is related anteriorly to the mylo-hyoid muscle. It is inserted 

 by a flat fasciculated tendon into the edge of the horizontal ramus, a little 

 distance above the symphysis. 



Action.^To depress the lower jaw and open the mouth. 



The Mylo-hyoid Muscles stretch across the intermaxillary space, and 

 form a support for the tongue. Each muscle arises from a hne on the 

 inner surface of the horizontal ramus behind its alveolar border ; and its 



