FACE AND FRONTAL REGION OF HEAD 129 



and the quadratics lahii sxiperioris immediately below their origins, and 

 turn them downwards towards the upper lip. When this has been done, 

 clear away the fatty tissue which lies on the deep aspect of the quadratus 

 labii superioris and secure the infra-orbital vessels and nerve, as they emerge 

 from the infra-orbital foramen. The infra-orbital plexus lies deep to the 

 quadratus labii superioris, and on the superficial aspect of the musculus 

 caninus. From the plexus three groups of branches are distributed : (i) 

 palpebral, which pass upwards to the lower eyelid ; (2) nasal, which run 

 medially to the nose ; and (3) labial, which descend to the upper lip. Either 

 by means of these branches, or more directly, the lower zygomatic twigs 

 of the facial nerve are distributed to the musculus zygomaticus, the muscles 

 of the lower eyelid, muscles of the nose, and the muscles of the upper lip. 



The mandibular branch or branches run anteriorly along the 

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

 As they pass anteriorly they lie deep to the triangularis, and 

 they communicate, under cover of it, with the mental branch 

 of the inferior alveolar (O.T. dental) nerve. To display this 

 communication the triangularis must be reflected, and the 

 mental vessels and nerves must be found as they emerge 

 from the mental foramen. 



Arteria Maxillaris Externa (O.T. Facial). The ex- 

 ternal maxillary artery is a tortuous vessel which enters the 

 face at the lower and anterior angle of the masseter, after 

 turning round the lower border of the mandibfe and'piercing 

 the deep fascia of the neck. From that point it runs 

 anteriorly and upwards to the angle of the mouth and then, 

 assuming a more vertical direction, it is prolonged upwards, 

 as the angular artery, to the medial commissure of the 

 eyelids, in the substance of the angular head of the quadratus 

 labii superioris. Immediately after its entrance into the face 

 it is comparatively superficial, being covered by skin, super- 

 ficial fascia, and platysma, and it is easily compressed against 

 the bone. More anteriorly it lies between the zygomaticus 

 superficially and the buccinator deeply, then between the 

 quadratus labii superioris and the caninus, and, as already 

 stated, its terminal part is usually embedded in the substance 

 of the quadratus labii superioris. 



Branches. The branches of the external maxillary artery 

 form two groups, a posterior and an anterior. The branches 

 of the posterior group pass posteriorly and are of small size. 

 They are distributed to the masseteric, buccal, and malar 

 regions where they anastomose witrTthe transverse facial/The 

 buccinator, and the infra-orbital arteries. 



The branches of the anterior group run anteriorly and re- 



VOL. II 9 



