286 THE MUSCLES OF THE HEAD AND NECK. 



infraorbital vessels and nerve emerge from the canal of the same name. Its inner border is 

 more or less united with the common elevator of the lip and nose. 



The levator anguli oris, or musculus caninns, arises in the canine fossa 

 immediately below the infraorbital foramen, and inclines downwards and slightly 

 outwards to the angle of the mouth, where some of the fibres are inserted into the 

 skin ; but the greater number decussate with the depressor anguli oris, and are 

 continued into the orbicularis muscle in the lower lip. 



Relations. At its origin this muscle is concealed by the proper elevator of the upper lip ; 

 its anterior surface supports the infraorbital nerve and artery, which separate it from the 

 preceding muscle ; the posterior surface lies on the superior maxilla and the buccinator 

 muscle. 



The ZYGOMATICI are two narrow and subcutaneous fasciculi of muscular fibres, 

 extending obliquely from the most prominent part of the cheek towards the angle of 

 the mouth, one being thicker and longer than the other. 



The zygomaticus minor, a very small muscle, arises from the anterior and 

 inferior part of the malar bone, and inclines downwards and forwards to terminate 

 by joining the outer margin of the levator labii superioris. 



The zygomaticus major arises from the malar bone near the zygomatic suture, 

 and descends to the angle of the mouth, where it is mainly inserted into the skin, in 

 small part also into the mucous membrane. 



Varieties. The zygomaticus minor is frequently absent ; or it may fall short of the 

 mouth, and be inserted into the fascia of the cheek. It may arise wholly or in part from the 

 orbicularis palpebrarum ; it has also been observed fused with the zygomaticus major, or the 

 levator labii superioris. or even united to the outer fibres of the frontalis (Eustachius). It has 

 frequently been found double. 



The zygomaticus major has also been found double, or it may be double merely at its 

 insertion. Sometimes it arises from the masseteric fascia below the zygoma. Absence of the 

 muscle has also been observed. 



The risorius (Santorini) consists of some very thin fasciculi, which commence 

 in the fascia over the masseter, or on the parotid gland, and extending trans- 

 versely inwards in the fat of the cheek, are inserted into the skin at the angle of 

 the mouth. 



Varieties. The risorius is often absent. It has been seen to arise from the integument 

 over the upper end of the sterno-mastoid, from the zygoma, from the external ear, and from 

 the fascia over the mastoid process. It has also been found double and even triple. 



The lower and lateral part of the face receives a superficial muscular covering 

 from the facial part of the platysma myoides, which is incorporated with the 

 muscles of the angle of the mouth and lower lip, and passes along with the super- 

 ficial fascia over the base of the jaw into the cervical portion of the muscle ; the 

 anterior portion of the cervical platysma, on the other hand, though continuous 

 externally with the facial, takes firm attachment to the base of the jaw for a length 

 of two inches or more external to the symphysis. 



The "buccinator muscle consists of a flat and thin but strong set of fibres in 

 contact with the mucous membrane, and forming a considerable part of the wall of 

 the mouth. It is attached by its upper and lower margins to the outer surface of 

 the alveolar parts of the maxillary bones, opposite the molar teeth, and by its pos- 

 terior margin to the pterygo-maxillary ligament, a narrow band of tendinous fibres, 

 which extends from the hamular process of the internal pterygoid plate to the rnylo- 

 hyoid ridge of the lower jaw close to the last molar tooth, and is placed between the 

 buccinator muscle and the superior constrictor of the pharynx (fig. 280, p. 305). 

 From these parts the fibres of the muscle are directed forwards, approaching each 



