DISSECTION OF THE HEAD AND NECK. 195 



and for the rest of its extent it is traversed by Wharton's duct — the 

 excretory duct of the gland. The superior extremity of the gland is 

 loosely maintained beneath the wing of the atlas ; the inferior extremity 

 is situated within the intermaxillary space, and is crossed outwardly by 

 the submaxillary artery. 



Wharton's Duct is formed by the union of small branches which 

 emanate from the gland structure along its anterior border. It descends 

 along that border, and at the lower extremity of the gland it crosses to 

 the inner side of the submaxillary artery, and is continued beneath the 

 tongue, where it will subsequently be followed in its course towards the 

 barb. 



The Digastricus (Plate 31). The upper belly of this muscle has 

 already been seen to arise from the styloid process of the occipital bone, 

 where it is confounded with the stylo-maxillaris muscle. It is succeeded 

 by an intermediate tendon, which plays through a perforation in the 

 tendon of the stylo-hyoid muscle, in front of which it joins the lower 

 belly. The lower belly has already been dissected in the intermaxillary 

 space, where it is inserted by tendinous slips into the posterior border of 

 the inferior maxilla, above the symphysis. 



Action. — To depress the lower jaw. 



The Stylo-hyoid (Plate 31). This muscle arises from the extreme 

 upper part of the hinder edge of the great cornu. Its inferior tendon is 

 perforated for the passage of the digastricus, and is inserted into the base 

 of the thyroid cornu of the hyoid bone. The external carotid emerges 

 between the belly of the muscle and the great cornu. 



Action. — It carries the base of the tongue and the larynx upwards and 

 backwards, by flexing the joint between the great and small cornua, and 

 the joint between the small cornu and the body. 



Directions. — Pin the lower extremity of the submaxillary gland and 

 Wharton's duct in position, and then remove the remainder of the gland 

 together with the stylo-hyoid, the digastricus, and the remains of the 

 stylo-maxillaris. This will expose the posterior part of the guttural 

 pouch, the pharynx, the larynx, the pharyngeal lymphatic glands, the 

 upper part of the external carotid artery (and its terminal branches — the 

 external and internal carotids, and the occipital), the superior cervical 

 ganglion of the sympathetic (and the upper part of the cervical cord), 

 the first parts of the 9th, 10th, 11th, and 12th cranial nerves, and the 

 inferior primary branch of the 1st cervical nerve. 



Pharyngeal Lymphatic Glands. These form an elongated cluster 

 situated at the upper part of the side of the pharynx. They are placed 

 on the course of all the lymphatic vessels of the head. 



The Common Carotid Artery (Plate 32) divides above the cricoid 

 cartilage of the larynx, and under cover of the submaxillary gland or 

 the stylo-maxillaris muscle, into three branches, viz., external carotid, 



