70 THE NERVOUS SYSTEM 



open, preferably by a gag, so as to tilt the coronoid process 

 forwards, and the needle is entered below the posterior part 

 of the zygomatic arch and immediately in front of the 

 temporo-mandibular joint (Fig. 39). It is passed medially and 

 slightly backwards for a distance of 4 cms. from the surface, 

 and the contents of the syringe may then be injected 

 (Symington). The masseter, temporal and both pterygoid 

 muscles are pierced in turn, and their bulk accounts for the 

 depth to which the needle must be thrust. As in the case 

 of the maxillary nerve, it is advisable to perform the operation 

 without an anaesthetic, as the severe pain caused by the 

 entrance of the point of the needle into the nerve is the surest 

 guide to the site of injection. Care must be taken not to pass 

 the needle in too far, as it may pierce the lateral wall of the 

 naso-pharynx or the terminal part of the auditory (Eustachian) 

 tube (p. 329). 



The Otic Ganglion is connected with the mandibular 

 nerve immediately below the foramen ovale. It receives 

 fibres not only from the trigeminal but also, through the lesser 

 superficial petrosal nerve (p. 92), from the facial and the 

 glosso-pharyngeal nerves. The efferent fibres are partly 

 secretory and partly motor. The secretory fibres join the 

 auriculo-temporal nerve, and are conveyed by it to the 

 parotid gland ; the motor fibres supply the tensor tympani 

 (p. 204) and the tensor veli palatini (tensor palati). It is not 

 yet certain whether the motor fibres originate in the motor 

 nucleus of the fifth or the seventh. 



The mandibular nerve is responsible for the innervation 

 of the MUSCLES OF MASTICATION. They include the temporal, 

 the masseter, the internal pterygoid, the external pterygoid, the 

 mylo-hyoid and the anterior belly of the digastric. 



The Temporal and the Masseter muscles elevate the 

 mandible and are rendered tense when the teeth are firmly 

 clenched. The contractions of the temporal muscle can be 

 appreciated best near its upper border, about 2 inches or 



