FIFTH PAIR OF NERVES. 



291 



anterior part of the nerve by the time it has 

 escaped from the cranium. 



The third division of the fifth nerve, after its 

 escape from the cranium, is situate in the 

 superior, posterior, and internal part of the 

 zygomatic fossa ; it is placed immediately be- 

 hind the external pterygoid muscle, before and 

 somewhat internal to the styloid process of the 

 sphenoid bone, internal to and on a line with 

 the anterior margin of the temporo-maxillary 

 articulation, and external to the Eustachian 

 tube. So soon as the inferior maxillary nerve 

 has entered the fossa, it gives off, immediately 

 beneath the superior wall of that fossa, a set 

 of branches remarkable for their source and 

 destination ; they proceed from the front of the 

 nerve; their regular number is five, but they 

 present variety in this respect, being in some 

 instances not so many at their origin, in others 

 amounting to six ; they vary also in the mode 

 in which they arise; for the most part they 

 are given off separately and branch off, as 

 rays, from the nerve, but at times the nerve 

 divides into two branches, a smaller anterior 

 one, and a larger posterior ; in such case the 

 anterior divides immediately into the branches, 

 which otherwise arise from the nerve itself. 

 These branches are the masseteric, the deep 

 temporals, the buccal, and the pterygoid nerves, 

 and they are ranged in succession from behind 

 forward, and from without inward ; the first is 

 external and posterior; to it succeed the tempo- 

 rals, then the buccal, and lastly the pterygoid. 



1 . The masseteric branch proceeds from the 

 anterior and outer part of the nerve; it passes out- 

 ward, nearly transversely, beneath the superior 

 wall of the temporal fossa, and in front of the 

 articular surface of the temporal bone ; it crosses 

 obliquely over the external pterygoid muscle, 

 at its outer extremity, between the muscle and 

 the wall of the fossa, and then inclines down- 

 ward through the sigmoid notch of the lower 

 jaw, in front of its neck, and of the insertion of 

 the external pterygoid muscle, and posterior to 

 the coronoid process and the tendon of the 

 temporal muscle. Having traversed the notch 

 it descends forward, external to the ramus of 

 the jaw, and passing between the two portions 

 of the masseter, divides into numerous ramifica- 

 tions, which are distributed altogether to that 

 muscle : while between the portions of the 

 masseter, it inclines from its posterior toward 

 its anterior margin, and its terminating filament 

 can be traced to the latter at the inferior part 

 of the muscle. This branch gives off, during 

 its course, some minor branches ; while in front 

 of the articulation of the jaw it gives one or 

 more filaments to the articulation ; in the next 

 place it gives a small branch to the posterior 

 part of the temporal muscle, and lastly it fre- 

 quently gives off the external or posterior deep 

 temporal nerve. 



2. The deep temporal branches are two; they 

 are distinguished into posterior and anterior or 

 external and internal. The anterior is the 

 larger. They present varieties in their num- 

 ber and mode of origin ; at times there is but 

 one, at others there are three ; in some instances 



they arise by a common origin ; in others, and 

 for the most part, separately, and in others 

 again the posterior or lesser branch is given off 

 either by the masseteric or the buccal nerve. 

 They both pass outward, in front of the tem- 

 poro-maxillary articulation, between the exter- 

 nal pterygoid muscle and the superior wall of 

 the zygomatic fossa; they then change their 

 direction and ascend in the temporal fossa, be- 

 tween the muscle and the surface of the fossa, 

 and divide into branches, which attach them- 

 selves to the temporal muscle, on its deep sur- 

 face, and are distributed, those of the posterior 

 to its posterior, and those of the anterior to its 

 middle and anterior parts. The two branches 

 frequently anastomose with each other as they 

 leave the zygomatic fossa. The anterior also 

 frequently communicates with or receives a 

 branch from the buccal nerve, and by one of 

 its anterior filaments it anastomoses with the 

 nerve resulting from the junction of the tempo- 

 ral branches of the lachrymal nerve and the 

 temporo-malar branch of the second division of 

 the fifth. This communication between the 

 three divisions of the fifth is however, accord- 

 ing to the elder Meek el, subject to variety; he 

 states that he has seen the communicating 

 branch of the anterior deep temporal at times 

 enter the orbit either through the malar bone, 

 or through the spheno-m axillary fissure, and 

 there unite with the conjoined branch of the 

 other two. 



3. The buccal nerve is the largest and the 

 principal of these branches ; it arises from the 

 front of the inferior maxillary nerve, next in or- 

 der after the anterior deep temporal, for the most 

 part a distinct and single branch ; but it is not 

 unusual to find the buccal nerve give off one or 

 both of the deep temporals, or in rare cases all 

 the three former branches: in some instances 

 also it arises double, the two filaments, of 

 which it is then composed, being separated by 

 a portion of the external pterygoid muscle. It 

 runs downward and forward, passing at first 

 either and for the most part through the exter- 

 nal or between the two pterygoid muscles, be- 

 neath the external and external to the internal ; 

 having traversed the pterygoid it descends in 

 front of its inferior part, internal to the coronoid 

 process of the lower jaw, and the inferior part 

 of the temporal muscle, next between the ten- 

 don of the temporal and the buccinator, then 

 between the anterior margin of the masseter 

 and the latter muscle, and finally emerging 

 from between them it inclines toward the angle 

 of the mouth, superficial to the buccinator and 

 beneath the dense expansion by which that 

 muscle is covered. During its descent it is 

 immersed in the fat which occupies the lower 

 part of the zygomatic fossa. The ramifications 

 which it gives off are numerous; first while 

 traversing and immediately after escaping 

 from the pterygoid it gives branches to the 

 muscle ; at the same time it gives off a 

 fasciculus of branches which pass outsvard, in 

 front of the external pterygoid to the internal 

 surface of the temporal muscle, at its inferior 

 part ; some of these descend with the muscle 



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