FIFTH PAIR OF NERVES. 



283 



arises, for the most part, from the ophthalmic 

 at the same time with its other branches ; 

 J. F. Meckel asserts that it arises more fre- 

 quently from a trunk common to rt and the 

 frontal ; but the contrary is maintained by 

 the elder Meckel ; he, however, states that it 

 arises frequently by two roots, one from the 

 ophthalmic, and a second from the frontal, and 

 once he has seen it derive a root from the tem- 

 poro-malar branch of the superior maxillary 

 nerve.* When it arises from the ophthalmic, it 

 is at its origin, inferior to the frontal, and exter- 

 nal to the nasal. Its course is forward and 

 outward at a very acute angle with the frontal ; 

 it enters the orbit through the foramen lacerum, 

 and from its origin until its entrance it is con- 

 tained in the dura mater lining the inner side 

 of the middle fossa of the base of the cranium, 

 beneath the lesser wing of the sphenoid bone : 

 in entering it passes above the origins of the 

 external rectus muscle, between it and the pe- 

 riosteum, and pursues its course along the 

 outer wall of the orbit, external to the superior 

 rectus and superior to the external, until it 

 reaches the lachrymal gland : it then passes 

 between the gland and the eyeball, and then 

 divides into branches. It is accompanied 

 through its course by the lachrymal artery. 

 The branches into which it divides are, for the 

 most part, three ; they enter the gland on its 

 ocular surface, traverse it and again escape 

 from it on its external aspect ; in their course 

 through the gland they divide and commu- 

 nicate with each other, and thus form within 

 it a plexus, from which numerous ramifications 

 are distributed to its substance. After having 

 supplied the gland the branches of the lachry- 

 mal emerge from it, and pursue two destina- 

 tions : one of them, which is for the most part 

 the first branch of the nerve, and is frequently 

 given off before it has reached the gland, de- 

 scends backward toward the spheno-maxillary 

 cleft, and joins the temporal branch of the 

 temporo-malar branch of the second division of 

 the fifth. In its course this branch passes first 

 between the external rectus muscle and the 

 outer wall of the orbit, then becomes attached 

 to the wall, and is either simply inclosed in the 

 periosteum, or contained in a groove or canal 

 m the orbitar process of the malar, or some- 

 times of the sphenoid bone; in this canal it meets 

 the branch of the temporo-malar, and from the 

 junction of the two results a filament, the des- 

 tination of which will be described under that 

 of the temporo-malar. This branch of the 

 lachrymal nerve is called the posterior or sphe- 

 no-majcillary : it might from its destination be 

 appropriately termed temporal: it frequently 

 gives off in its descent a filament, which passes 

 forward, escapes from the orbit beneath the ex- 

 ternal canthus, and is distributed as the other 

 branches of the lachrymal are. The remaining 

 branches of the lachrymal escape from the 

 orbit into the upper eyelid, beneath the exter- 



* [According to Cruveilhier the lachrymal nerve 

 very often arises by two filaments, one from the 

 ophthalmic, the other from the fourth nerve, and 

 Swan describes this as the normal condition. 

 Cruveilhier, Anat. Deter, t. iv. p. 911. ED.] 



nal part of the superciliary arch. They give 

 off numerous filaments, which are distributed 

 to the structures of the lid, the conjunctiva, the 

 orbicular muscle, and the integument : the ex- 

 ternal of them, which are the largest, not only 

 supply brandies to the upper, but descend be- 

 hind the external commissure of the lids into 

 the lower one, which they supply at its outer 

 part; they are also distributed to the superfi- 

 cial parts on the malar region. They anasto- 

 mose with the frontal nerve, the superficial 

 temporal, the facial, the temporo-malar, and 

 the infra-orbital nerves. 



The second division of the fifth. This has 

 been called also by Winslow, in consequence 

 of its distribution, the superior maxillary nerve. 

 It is the second trunk connected with the 

 Gasserian ganglion, and is intermediate to the 

 others, both in size and situation ; larger than 

 the first, and placed beneath and external to it; 

 smaller than the third, and situate internal, 

 superior and anterior to it ; it is attached to the 

 middle of the anterior convex margin of the 

 ganglion; at first it is flattened, wide, and of a 

 cineritious tint ; but, as it proceeds, it becomes 

 contracted in width, of a cylindrical form, and 

 presents a white colour. At leaving the gan- 

 glion it is joined by a filament of the sympa- 

 thetic. This has been seen by Munniks* and 

 Laumonier,f and is stated by Meckel junior, 

 on the authority of the latter. The communi- 

 cation between the sympathetic and the second 

 and third divisions is called in question by 

 Arnold.^ That with the third the author has 

 not yet made out, but that with the second he 

 has found satisfactorily established by a fila- 

 ment from the branch of the sympathetic which 

 joins the sixth nerve : this filament connects the 

 sixth to the second division of the fifth, and is 

 short, but grosser than those which join the first : 

 in consequence of the irregularity which pre- 

 vails in the arrangement of the sympathetic 

 system, the description here given may not 

 apply in other instances. 



The course of the second division of the fifth 

 within the cranium is short; it is directed for- 

 ward, slightly outward and downward, toward 

 the superior maxillary or the foramen rotundum 

 of the sphenoid bone; having reached that 

 foramen it enters the canal, of which it is the 

 aperture, and escapes through it from the 

 cranium. While within the latter the nerve 

 is contained in a sheath of dura mater, and 

 rests in a shallow channel on the body of 

 the sphenoid bone, at its junction with the 

 great ala. From the cranium it enters the 

 spheno-maxillary fossa, and crosses that fossa 

 at its superior extremity, from behind forward, 

 inclining still downward and outward, though 

 but slightly ; its course across the fossa is also 

 very short, extended between the root of the 

 pterygoid process behind and the highest part 

 of the posterior wall of the maxillary antrum 

 before; having traversed the superior part of 

 the fossa it enters the infra-orbital canal, through 



* De Orisrine nervi intercostalis. 

 t Roux, Journ. de Med. t. xciii. 

 t Journ. Cornp. t. xxiv. 



