20 HEAD AND NECK 



That small nerve pierces the zygomatic bone a short distance 

 below the lateral border of the orbit. 



The lower filaments are larger. They run forwards along 

 the lower border of the zygomatic arch, under cover of the 

 musculus zygomaticus and the infra-orbital part of the 

 quadratus labii superioris, and deep to the latter they com- 

 municate with the infra-orbital branch of the maxillary division 

 of the trigeminal nerve, forming with it the infra-orbital plexus. 



The buccal branch or branches run towards the angle of 

 the mouth. At the anterior border of the masseter they com- 

 municate, around the anterior facial vein, with the buccinator 

 branch (O.T. long buccal) of the third division of the tri- 

 geminal, and they supply the buccinator and the orbicularis 

 oris. 



The mandibular branch or branches run forwards along the 

 mandible to be distributed to the muscles of the lower lip. 

 They pass deep to the triangularis, and they communicate, 

 under cover of it, with the mental branch of the inferior 

 alveolar (O.T. dental) nerve. 



The cervical branch after its exit from the lower end of 

 the parotid gland runs downwards and forwards to supply 

 the platysma and to communicate with the nervus cutaneus 

 colli, but since neither the terminal branches nor the com- 

 munication can be seen at present they will be displayed at 

 a later stage of dissection (see p. 122). 



Dissection. After the branches of the facial nerve, the 

 external maxillary artery and the anterior facial vein have been 

 studied, the dissection of the deeper muscles and the deeper 

 vessels and nerves must be proceeded with ; but the supra- 

 orbital and supra-trochlear nerves, and the supra-orbital vessels, 

 may be left till the scalp is dissected (p. 47). 



First clean the caninus muscle which lies deep to the infra- 

 orbital plexus and descends to the angle of the mouth, where it 

 blends with the orbicularis oris. Then clean the remains of the fat 

 from the surface of the buccinator, and as the fat is being removed 

 note the small molar glands which lie in it and the strong deep 

 bucco-pharyngeal fascia which covers the muscle. The ducts 

 of the molar glands pierce the bucco-pharyngeal fascia and the 

 buccinator and open into the vestibule of the mouth. Clean 

 away the bucco-pharyngeal fascia and define the attachments 

 of the buccinator to the maxilla and the mandible, and trace its 

 fibres forwards to the angle of the mouth, where they blend with 

 the orbicularis oris. 



Musculus Caninus (O.T. Levator Anguli Oris). The 

 caninus is concealed by the lower part of the orbicularis 



