FIFTH PAIR OF NERVES. 



293 



into three branches, viz. the lingual, the inferior 

 maxillary, and the superficial temporal, and 

 such is the mode of division mentioned by 

 the elder Meckel. The writer has before him 

 an instance of another mode ; the inferior 

 maxillary arises by two roots, and the original 

 trunk divides into two parts; one common to 

 the lingual, and one root of the maxillary; 

 the other to the superficial temporal and the 

 other root: the superficial temporal is thus, 

 in this instance, equally an original branch 

 as the others, and is connected to the maxillary 

 by a filament, which it gives off soon after 

 its origin, while the maxillary is also connected 

 in the usual mode to the lingual : the maxillary 

 artery, however, passes through the loop formed 

 by the two roots of the former nerve. 



The length of the third division from the 

 ganglion to its bifurcation is about three fourths 

 of an inch, one fourth contained within the 

 bone during its escape from the cranium, and 

 the other two between the aperture externally 

 and the division. When it divides into two, 

 the branches are, at times, of the same size, 

 but for the most part the inferior maxillary 

 is the larger; they descend at first in close 

 apposition with each other, but as they proceed 

 they gradually separate, the lingual branch 

 inclining inward and forward, the inferior 

 maxillary outward, in the course of the original 

 nerve, in order to gain the aperture of the 

 dental canal ; they thus leave between them 

 an angular interval, acute above, through 

 which the internal maxillary artery for the most 

 part passes. In their descent they cross, at 

 right angles, the artery internal to the origin 

 of the middle meningeal branch : in doing so 

 either they pass both behind the vessel, or the 

 lingual branch passes before, and the inferior 

 maxillary behind it. The two nerves are most 

 frequently connected, soon after their origin, 

 by a short and delicate branch, which passes 

 from the inferior maxillary to the lingual, and 

 forms, with the nerves, a triangle, through 

 which the artery passes in those instances in 

 which the lingual descends before it. 



The nerves are situate internal to the neck 

 and ramus of the jaw, between the pterygoid 

 muscles, posterior and inferior to the external, 

 external and anterior to the internal ; and they 

 are contained in a triangular space included 

 between the two muscles and the jaw, bounded 

 superiorly by the external, beneath and in- 

 ternally by the internal pterygoid, and externally 

 by the jaw ; through this space they pass from 

 above downward, the lingual from behind 

 forward, and from without inward, the maxil- 

 lary from within outward, toward the aperture 

 of the dental canal, and holding the mutual 

 relation already indicated, the lingual anterior 

 and internal, the maxillary posterior and ex- 

 ternal. 



Before pursuing these branches of the third 

 division further, it will be well to describe 

 the superficial temporal nerve. This branch 

 has been viewed differently by different autho- 

 rities; by some it is accounted one of the 

 former set, the superior anterior branches of 

 the third division ; by Meckel it is described 



as one of three, into which the continuation 

 of the nerve divides. It arises for the most 

 part by two, and in some instances by three, 

 roots ; a larger one from the inferior dental 

 nerve, and a smaller from the trunk of the 

 third division itself, given off at the same 

 time with its superior branches, and deri- 

 ved from the same source; the two roots 

 forming together a loop, through which the 

 middle meningeal artery ascends: in conse- 

 quence of this mode of origin it appears better 

 to describe it thus separately, and not to refer 

 it to either of the sets described. It has, 

 however, been already explained that in some 

 cases it appears to be an original branch of 

 the third division, one of three into which it 

 finally divides. 



The nerve runs outward, backward, and 

 somewhat upward, behind the external ptery- 

 goid muscle, toward the back of the neck of 

 the lower jaw; it then passes behind it and 

 the condyle, between them and the auditory 

 canal, traversing tlie posterior part of the 

 glenoidal cavity of the temporal bone, and 

 imbedded in the process of the parotid gland, 

 which occupies it. 



The superficial temporal nerve, while within 

 the ramus of the jaw, pursues a course nearly 

 the reverse of that of the trunk of the internal 

 maxillary artery in the first part of its course. 

 At first it is situate before the tensor palati 

 muscle, between it and the external pterygoid ; 

 then it passes between the internal lateral 

 ligament of the maxillary articulation and the 

 neck of the jaw, situate at the same time 

 above and in contact with the artery ; and 

 lastly, it is situate behind the condyle of the 

 jaw, between it and the meatus auditorius, 

 and involved in the parotid. 



The nerve gives off numerous branches; 

 when it has reached the situation last described, 

 it breaks up at once into a leash of branches, 

 which pass off in different directions : of these 

 two, at times only one, are destined for the 

 interior of the meatus auditorius ; they ascend 

 toward the canal, become attached to its ex- 

 terior, and pass through the fibrous structure of 

 the tube, close to its connection with the osseous 

 portion : having thus gained its interior, they 

 are distributed to its lining membrane, its 

 sebaceous follicles, and the membrane of the 

 tympanum. Before entering the tube they give 

 some delicate filaments to its exterior; these 

 branches may be called the internal auricular. 



Others, the smallest which the nerve gives 

 off, descend along the external carotid artery, 

 are in part distributed to the parotid gland, 

 and establish upon the artery a manifest com- 

 munication with branches of the sympathetic. 

 Its next branches, two in number, pass out- 

 ward through the substance of the parotid, 

 behind the neck of the jaw ; one external or 

 superficial, the other internal to the temporal 

 artery; and turning forward round the posterior 

 margin of the jaw, either they both, having 

 given some fine ramifications to the gland, 

 join the tern poro- facial branch of the portio 

 dura, immediately before its division, or one 

 of them joins the facial branch of the tern- 



