THE FASCLE AND MUSCLES OF THE HEAD 255 
with the posterior deep pectoral muscle to the medial tuberosity of the humerus. 
Posteriorly it forms a fold, which, covered by the skin, forms the fold of the flank, 
and ends on the fascia above the stifle. The dorsal limit of the muscle corresponds 
approximately with a line drawn from the posterior angle of the scapula to the fold 
of the flank. Ventrally the two muscles are about a handbreadth apart in the um- 
bilical region. Further forward they diverge, so as to overlap the posterior deep 
pectoral muscle only to a small extent. Here the cutaneous muscle is closely ad- 
herent to the pectoral and contains the external thoracic vein. Posteriorly they 
diverge to the fold of the flank. 
The muscle is in general closely adherent to the skin and its contraction twitches 
the skin, thus getting rid of insects or other irritants. 
THE FASCIZ AND MUSCLES OF THE HEAD 
The muscles of the head (Mm. capitis) may be divided into three groups, viz.: 
(1) Superficial muscles, including the cutaneous muscle and those of the lips, cheeks, 
nostrils, eyelids, and external ear; (2) the orbital muscles; (8) the mandibular 
muscles; (4) the hyoid muscles. 
The superficial fascia forms an almost continuous layer, but is very scanty 
around the natural orifices. It contains a number of the thin superficial muscles, 
so that care must be exercised in removing the skin. Over the frontal and nasal 
bones the fascia blends with the pericsteum. 
The deep fascia is of special interest in three regions. The temporal fascia 
(Fascia temporalis) covers the temporalis muscle, and is attached to the parietal 
and frontal crests medially, and to the zygomatic arch laterally. The buccal fascia 
(F. buccalis) covers the buccinator muscle and the free part of the outer surface of 
the ramus of the mandible. It is attached to the facial crest, and posteriorly it 
forms a band (Raphé pterygomandibulare) which stretches from the hamulus of the 
pterygoid bone to the mandible behind the last molar tooth. It is directly continu- 
ous with the pharyngeal fascia (F. pharyngea), which is attached to the great and 
thyroid cornua of the hyoid bone and the thyroid cartilage of the larynx; it covers 
the lateral walls of the pharynx, and blends dorsally with the median raphé of the 
constrictor muscles of the latter. 
Cutaneus faciei—This has been described (p. 254). 
MUSCLES OF THE LIPS AND CHEEKS 
1. Orbicularis oris——This is the sphincter muscle of the mouth; it is con- 
tinuous with the other muscles which converge to the lips. It lies between the 
skin and the mucous membrane of the lips, and is intimately adherent to the 
former. Most of the fibers run parallel to the free edges of the lips and have no 
direct attachment to the skeleton. 
Action.—It closes the lips. 
Blood-supply —Palato-labial, facial, and mental arteries. 
Nerve-supply.—F acial nerve. 
2. Levator nasolabialis..—This thin muscle lies directly under the skin, and 
chiefly on the lateral surface of the nasal region. 
Origin.—The frontal and nasal bones. 
Insertion—(1) The upper lip and the lateral wing of the nostril; (2) the com- 
missure of the lips. 
Action.—(1) To elevate the upper lip and the commissure; (2) to dilate the 
- nostril. 
1Also termed the levator labii superioris alzeque nasi. 
