284 



FIFTH PAIR OF NERVES. 



which it is transmitted, in company with the in- 

 fra-orbital artery, to the face. In the canal it is 

 situate in the floor of the orbit or the roof of the 

 antrum, separated from each cavity, more or 

 less perfectly, by a thin lamina of bone ; its 

 course within the canal is by much its longest 

 stage; as the nerve approaches the anterior 

 extremity of the canal, it inclines inward, and 

 thus its course is rendered a curve, convex 

 outward. In this respect, however, it pre- 

 sents varieties, dependant upon the transverse 

 dimensions of the face, which being great, 

 the course of the nerve is more curved and 

 vice versa, it being sometimes nearly straight. 

 From the time that the nerve enters the canal, 

 it has been called infra-orbital; but, inasmuch 

 as that part of it is manifestly but the con- 

 tinuation of the trunk, and names are already 

 rather too numerous than otherwise, it would 

 be better if that one were discarded. From 

 the infra-orbital canal the nerve escapes through 

 its anterior aperture into the face ; that aperture 

 corresponds, for the most part, to the point of 

 junction of the two external with the internal 

 third of the inferior margin of the orbit, and is 

 from a quarter to half an inch below it; its 

 situation, however, is not uniform; in some 

 skeletons it will be found to correspond nearly 

 to the middle of the margin, and this circum- 

 stance is worthy of attention, in consequence 

 of its relation to the operation for the division 

 of the nerve. 



At its escape from the canal the nerve is 

 concealed by the lower margin of the orbicu- 

 laris palpebrarum and by the levator labii supe- 

 rioris muscle, beneath which it is placed, and 

 it is above the upper extremity of the origin of 

 the levator anguli oris : immediately after its 

 escape it separates into a number of branches, 

 which go off in different directions to their 

 several destinations, but principally downward. 



The branches which the second division 

 gives off are the temporo-malar, the spheno- 

 palatine, the posterior superior dental, the an- 

 terior superior dental, and the facial branches. 

 While within the cranium the nerve gives off 

 no branch. 



1. The first branch given off by the second 

 division, the temporo-malar, has been called 

 cutaneous malar by the elder Meckel ; it has 

 been also called orbitar, but without good 

 reason ; the name temporo-malar fully expresses 

 its distribution. This branch is given off by 

 the nerve, either while yet within the canal, 

 through which it escapes from the cranium, or 

 after it has entered the spheno-maxillary fossa ; 

 it is one of its smallest branches ; it passes for- 

 ward through the fossa, toward the spheno- 

 maxillary cleft, enters the orbit through the 

 cleft, and then pursues its course forward and 

 outward, along the floor of that region, beneath 

 the inferior rectus muscle, and about the mid- 

 dle of it divides into two branches ; an exter- 

 nal, the temporal, and an anterior, the malar. 



Before entering the orbit it sometimes gives 

 off a small branch, which enters that cavity 

 through the periosteum of the posterior part of 

 the orbitar process of the sphenoid bone, and 

 joins the lachrymal branch of the first division, 



presenting one of the instances of a second root 

 to that branch, as described by the elder Meckel. 



The external temporal branch passes toward 

 the outer wall of the orbit, ascends between it 

 and the external rectus muscle ; then becomes 

 attached to the wall, and continues its course 

 either through the periosteum, or in a groove, 

 or at times through a canal in the orbitar pro- 

 cess of the malar, or occasionally of the sphe- 

 noid bone ; here it is joined by the posterior 

 temporal branch of the lachrymal nerve, the 

 third branch of the first division : the conjoined 

 branch is then transmitted into the temporal 

 fossa, through an aperture on the temporal sur- 

 face of the orbitar process of the malar bone ; 

 there it is joined by a small branch of the an- 

 terior deep temporal branch of the inferior 

 maxillary or third division of the fifth, and 

 plunging among the fibres of the temporal 

 muscle, it is distributed to them in common 

 with the filaments of the deep temporal ; a 

 filament or filaments of it gain the superficial 

 surface of the muscle, perforate its aponeurosia, 

 become subcutaneous, and are distributed su- 

 perficially upon the temple, communicating 

 with filaments of the portio dura, and of the 

 superficial temporal branch of the third divi- 

 sion. The temporal branch of the temporo- 

 malar is sometimes double, or divides into two, 

 one communicating with the branch of the 

 lachrymal, the other transmitted to the temple. 



The malar branch pursues the course of the 

 original nerve, until it has reached nearly to 

 the anterior margin of the orbit, at its inferior 

 external angle ; then it enters, either single or 

 divided into two, the corresponding canal or 

 canals, by which the malar bone is perforated, 

 and through them is transmitted outward and 

 forward to the malar region of the face. Its 

 ramifications are distributed to the inferior ex- 

 ternal part of the orbicularis palpebrarum, and 

 to the integuments of the malar region ; they 

 communicate with those of the portio dura, of 

 the superficial temporal and lachrymal nerves, 

 and of the palpebral branches of the second 

 division. Before reaching the malar canals, 

 the malar branch frequently gives off one or 

 more filaments, which ascend to the lachrymal 

 gland, unite with those of the lachrymal nerve,, 

 and follow a similar distribution. 



2. The branches, which are given off next by 

 the second division of the fifth, are those by 

 which the nerve is connected to the spheno- 

 palatine ganglion ; they are hence denominated 

 the spheno-palatine ; the ramifications derived 

 from them, or from the ganglion with which 

 they are connected, are distributed to the nos- 

 tril and the palate, and they may hence with 

 more propriety be termed the naso-palatine, 

 an appellation which is the more appropriate, 

 since it is already applied to the corresponding 

 branch of the second division of the fifth in 

 other animals. It is at the same time to be 

 borne in mind that a difficulty has been created 

 in this matter by the application of the epithet 

 in question to certain secondary branches, to be 

 mentioned by and-by ; but the latter use of the 

 term oupht to be discarded. They are irregular 

 in number, there being sometimes but one, a-t 



