62 TOPOGRAPHICAL ANATOMY OF THE 



vessel that follows the auditory (Eustachian) tube aud gains the middle 

 ear by the petro- tympanic fissure. 



(4) A. onenivgea media. — The middle meningeal artery is also small 

 aud arises from the internal maxillary as it is approaching the entrance 

 to the alar canal. It at once gains the cranium by the foramen spinosum. 



(5) A. temiwralis pivfunda posterior. — The posterior deep temporal 

 artery arises at the entrance to the alar canal and thence passes upwards 

 and backwards underneath the temporal muscle. It anastomoses with 

 the middle meningeal and superficial temporal arteries, and supplies a 

 branch to the masseter muscle. 



N. MA.ND1BULARIS. — The fifth cerebral, or trigeminal, nerve divides 

 into three parts while still within the cranium, and each part leaves the 

 cranium by a different foramen. The three nerves formed by the 

 trio-eminal are the ophthalmic, the maxillary and the mandibular ; and it 

 is the last-named that can be examined at the present time. In view 

 of its distribution, it should be remembered that the mandibular ^ 

 nerve differs from the ophthalmic and the maxillary in that, though 

 mainly composed of sensory fibres, it contains motor fibres as well. 



The mandibular nerve is of large size and leaves the cranium by the 

 foramen ovale. Immediately on its exit from the foramen it divides 

 into a number of branches of varying size. 



(1) N. r^iassetericus. — The masseteric nerve curves rouad the front 

 of the mandibular joint in company with a tributary of the transverse 

 facial vein, and traverses the mandibular notch to reach the masseter 

 muscle. The terminal part of its course was seen during the removal 

 of the masseter. 



(2) Nn. temporales iwofundi. — The deep temporal nerves are 

 o-enerally two in number, and usually arise from the mandibular in 

 common with the masseteric nerve. They pass upwai'ds and forwards 

 to enter the temporalis muscle. 



(3) N. 'pterygoidcus. — The pterygoid nerve is the smallest branch 

 of the mandibular. It supplies the pterygoid muscles. 



A small, flat, oval ganglion — the otic'^ ganglion (ganglion oticum) — 

 is placed at the origin of the pterygoid nerve, where it rests upon the 

 tensor of the soft palate. The ganglion receives motor fibres from the 

 pterygoid nerve, sensory fibres from the facial and glosso-pharyngeal 

 nerves by way of the lesser superficial petrosal nerve, and sympathetic 

 filaments from the plexus about the internal maxillary artery. Delicate 

 nerves pass from the ganglion to the tensor tympaui, the tensor of the 

 soft palate and the auditory tube. 



1 Mandibuhim [L.], the lower jaw. 



2 ciruo's (oticos) [Gr.], iJertaining to the ear {ois\ 



