THE TRIGEMINAL NERVE 69 



(orbital) nerve, which communicates with the lacrimal (p. 65) 

 and emerges as two small branches to supply the skin of the 

 face behind the eye (Fig. 37). The communicating branch 

 conveys to the lacrimal the s-ecreto-motor fibres for the 

 lacrimal gland. These fibres probably emerge from the 

 brain-stem with the facial nerve, and pass by the greater 

 superficial petrosal to the spheno-palatine ganglion and the 

 maxillary nerve. 



In this situation, also, the maxillary gives off the posterior 

 superior alveolar (dental) nerve, which is distributed to the 

 molar teeth of the maxilla. It then enters the infra-orbital 

 canal in the floor of the orbit (Fig. 38) and supplies the 

 remaining maxillary teeth by means of the middle and the 

 anterior alveolar branches. Finally, the maxillary nerve 

 emerges from the infra-orbital foramen as the infra-orbital 

 nerve and appears on the face. 



The infra-orbital nerve breaks up into a large number of 

 branches. They supply (i) The skin and conjunctiva of 

 the lower eyelid \ (2) the skin on the postero-lateral aspect of 

 the nose ; (3) the skin and mucous membrane of the upper lip ; 

 (4) the skin and mucous membrane of the cheek. In addition, 

 the infra-orbital nerve supplies sensory fibres to a large 

 number of the facial muscles (p. 84). 



3. The MANDIBULAR NERVE carries off the whole of the 

 motor root of the trigeminal and, in addition, it contains a 

 large number of sensory fibres. It arises from the lateral 

 part of the semilunar ganglion, and leaves the interior 

 of the skull by passing downwards through the fora- 

 men ovale (Fig. 35). This course brings it at once into 

 the region of the pterygoid muscles, and, immediately below 

 the skull, the nerve lies between the external pterygoid, on the 

 lateral side, and the lateral wall of the naso-pharynx, on the 

 medial side. 



Corrosive fluids may be injected around the nerve in this 

 part of its course, and they will affect it above the point where 

 the important sensory branches arise. The mouth is held 



