MUSCLES OF THE LIPS AND CHEEKS 213 



often termed the head (Caput). Muscles having two or more heads arc called 

 biceps, triceps, etc. Digastric muscles are those which have two bellies joined by 

 an intermechate tendon. Ring-like muscles which circumscribe openings are 

 termed sphincters, on account of their action. 



6. The relations are, of course, important on surgical grounds. 



7. The nerve-supply is of clinical interest, and is important for the determina- 

 tion of homologies. 



FASCIA AND MUSCLES OF THE HORSE 

 PANNICULUS CARNOSUS 

 The panniculus camosus (Musculus cutaneus) is a thin muscular layer de- 

 veloped in the superficial fascia. It is intimately adherent in great part to the skin, 

 but has very little attachment to the skeleton. It does not cover the entire body, 

 and may be conveniently divided into facial, cervical, thoracic, and abdominal 

 portions, each of which will be described with the muscles of the corresponding 

 region. 



The Fascia and Muscles of the Head 



The muscles of the head may be divided into three groups, viz. : (1) Superficial 

 muscles, including the panniculus and those of the lips, cheeks, nostrils, eyelids, 

 and external ear; (2) the orbital muscles; (3) the muscles of mastication. 



The superficial fascia forms an almost continuous layer, but is verj' 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 periosteum. 



The deep fascia is of special interest in three regions. The temporal fascia 

 covers the temporalis muscle, and is attached to the parietal and frontal crests 

 internally, and to the zygomatic arch externally. The buccal fascia covers the 

 buccinator muscle and the free part of the outer surface of the ramus of the jaw. 

 Superiorly it is attached to the facial crest, and posteriorly it forms a band (Liga- 

 mentum pterygomandi1)ulare) which stretches from the hamulus of the pterygoid 

 bone to the mandible behind the last molar tooth. It is directly continuous with 

 the pharyngeal fascia, which is attached to the great and thyroid cornua of the 

 hyoid bone, covers the lateral walls of the pharynx, and blends dorsally with the 

 median raphe of the constrictor muscles of the latter. 



SUPERFICIAL MUSCLES 

 1. Panniculus camosus. — The facial panniculus (M. cutaneus faciei) consists 

 of a thin and usually incomplete muscular stratum, which covers the submaxillary 

 space and the masseter muscle. A branch from it passes forw^ard to the angle of 

 the mouth and blends with the orbicularis oris; this part (M. cutaneus labiorum) 

 retracts the angle of the mouth. (A number of the superficial muscles of the face 

 may be considered modified parts of the panniculus, e. g., the corrugator supercilii, 

 malaris, zygomaticus, etc.) 



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 



