THE HEAD AND NECK. 2277. 
(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. 
({) 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. It 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. 
