The Head and Xeck. 237 



(e) The buccinator is a broad stout band of fibres enclosing the 

 cheek and attached to the alveolar borders of the upper jaw 

 and mandible. 



(f) The caninus. Origin: Lateral border of the upper jaw. 

 Insertion: Hairy portion of the mucous membrane of the 

 mouth. The muscle is very broad, but short and extremely 

 thin. 



(g) The quadratus labii inferioris. Origin: Ventral border 

 of the mandible. Insertion: Skin of the lower lip. 



(h) The mentalis. The muscle surrounds the anterior portion 

 of the mandible behind the incisor teeth. It is attached 

 externally to the skin of the lower lip through the insertion 

 portion of the quadratus labii inferioris, which largely 

 overlies it. 



Because of the great size and mobility of the ears, the cutaneous 



auricular muscles, comprising some twenty different members, are 



especially well developed. These muscles are not individually described, 



but their development should be noted in contrast to the vestigial 



character of the ear muscles in man. 



3. Dissection on the ventral surface of the neck to free the 



external jugular vein and its tributaries. The cervical fascia and a 



portion of the parotid gland must be removed. 



The external jugular vein v. jugularis externa) is formed 

 behind the angle of the mandible by the union of the anterior and 

 posterior facial veins. It passes backward in a superficial position 

 to the superior thoracic aperture. Its connections in the lower part 

 of the neck comprise the transverse scapular vein (v. transversa 

 scapulae) of the shoulder and its union with the vein of the other 

 side by the transverse jugular vein (v. jugularis transversa) (Fig. 

 82). 



The posterior facial vein (v. facialis posterior) is formed below 

 the base of the ear by the union of the superficial and deep 

 temporal veins of the temporal region, the inferior ophthalmic 

 vein, from the posterior portion of the orbit, and the anterior 

 auricular vein from the ear. 1 1 passes downward in the substance 

 of the parotid gland, and in its first portion is covered by the 

 root of the facial nerve. Immediately below the latter it 

 receives the posterior auricular vein from the ear and back of 

 the head. 



