942 



THE NERVOUS SYSTEM 



(e) The superficial temporal branches supply the integument of the greater part of the tem- 

 poral region, and anastomose with the temporal branch of the facial nerve. 



THE MASTICATOR NERVE (Fig. 737) 



The masticator nerve (rnotor root or portio minor of trigeminus). The fibres 

 of the masticator nerve spring from two nuclei, a slender upper or mesencephalic 

 nucleus and a clustered lower or chief nucleus. The fibres arising in the mesen- 

 cephalic nucleus descend along the lateral aspect of the nucleus to the pons as 

 the descending or mesencephalic root;* here they join the fibres from the chief motor 

 nucleus and issue with them from the side of the pons in from six to ten root 

 filaments. These blend to form the nerve, which is from one and a half to two 

 millimetres broad. At the point where it emerges from the pons the nerve is in 

 front of and ventral to the root of the trigeminus and it is separated from the 

 latter by a few of the transverse fibres of the pons which constitute the lingula of 

 Wrisherg. From its superficial exit from the pons, the masticator nerve passes 

 upward, lateralward, and forward in the posterior fossa of the cranum, and along 

 the medial and anterior aspect of the trigeminus, to the mouth of Meckel's cave. 

 In this cavity it runs lateralward below the semilunar (Gasserian) ganglion to the 

 foramen ovale, through which it passes to join the mandibular division of the 



Fig. 737. — Schematic Representation of the Masticator Nerve and its Branches 

 (in Black). Lateral view. Modified from Spalteholz. 

 Gasserian ganglion 

 Masticator nerve / External pterygoid nerve 



Auriculo-temporal nerve \ 



', \ 



Internal maxillary artery^ 



Posterior deep 

 temporal nerve 



Anterior deep 

 temporal nerve 



Internal pterygoid 

 nerve 



Masseter nerve 



Buccinator nerve 



Lingual nerve -- 

 Inferior alveolar nerve -- 



External carotid artery -" 

 Mylo-hyoid nerve --■' 



trigeminus immediately outside and below the base of the skull. The nerve is 

 purely motor and its fibres are devoted almost wholly to the muscles having to do 

 with mastication. 



Central connections. — The nuclei of origin of the masticator nerve are connected with the 

 lower part of the somsesthetic area of the cerebral cortex of the opposite side by the pyramidal 

 fibres descending in the genu of the internal capsule, and they are associated with the sensory 

 nuclei of other cranial nerves through the reticular formation and by the medial longitudinal 

 fasciculus. 



Branches. — Almost immediately after joining the trunk of the mandibular 

 nerve, most of the fibres of the masticator leave it to form the greater part of the 

 so-called anterior portion of the mandibular. However, one branch of masticator 

 fibres, the nerve to the internal pterygoid muscle, is given off from the mandibular 

 just before its division into anterior and posterior portions. The masticator 



* Recent investigations indicate that the mescnophalic root is not wholly motor but at 

 least in part sensory in character, and thus belongs partly to the trigeminal nerve, (See 

 page 829.)' 



