BRANCHES OF THE FIFTH XERVE. 809 



Wharton's duct, some being lost in the submaxillary gland. The branch of com- 

 munication from the lingual to the fore part of the ganglion is by some regarded 

 'ranch of distribution, by which filaments of the chorda tympani pass from 

 the ganglion to the nerve, and by it are conveyed to the sublingual gland and the 

 tongue. 



Surface Marking. It will be seen from the above description that the three terminal 

 branches of the three divisions of the fifth nerve emerge from foramina in the bones of the skull 

 and face on to the face : the terminal branch of the first division emerging through the supra- 

 orbital foramen : that of the second through the infra-orbital foramen ; and the third through 

 the mental foramen. The supra-orbital foramen is situated at the junction of the internal 

 and middle third of the supra-orbital arch between the internal and external angular processes. 

 It' a straight line is drawn from this point to the lower border of the inferior maxillary bone, so 

 that it passes between the two bicuspid teeth in both jaws, it will pass over the infra-orbital and 

 mental foramina, the former being situated about one centimetre (two-fifths of an inch) below the 

 margin of the orbit, and the latter varying in position according to the age of the individual. 

 In the adult it is midway between the upper and lower borders of the inferior maxillary bone ; 

 in the child it is nearer the lower border ; and in the edentulous jaw of old age it is close to the 

 upper margin. 



Surgical Anatomy. The fifth nerve may be affected in its entirety, or its sensory or motor 

 root may be affected, or one of its primary main divisions. In injury to the sensory root there is 

 anaesthesia of the whole of the side of the face on the side of the lesion, with the exception of 

 the skin over the parotid gland ; insensibility of the conjunctiva, followed by destructive inflam- 

 mation of the cornea, partly from loss of trophic influence, and partly from the irritation pro- 

 duced by the presence of foreign bodies on it. which are not perceived by the patient, and there- 

 fore not expelled by the act of winking ; dryness of the nose, loss to a considerable extent of the 

 sense of taste, and diminished secretion of the lachrymal and salivary glands. In injury to the 

 motor root there is impaired action of the lower jaw from paralysis of the muscles of mastication 

 on tbe affected side. 



The fifth nerve is often tbe seat of neuralgia, and each of the three divisions has been 

 divided or a portion of the nerve excised for this affection. The supra-orbital nerve may be 

 exposed by making an incision an inch and a half in length along the supra-orbital margin below 

 the eyebrow, which is to be drawn upward, the centre of the incision corresponding to the supra- 

 orbital notch. The skin and Orbicularis palpebrarum having been divided, the nerve can be 

 easily found emerging from the notch and lying in some loose cellular tissue. It should be drawn 

 up by a blunt hook and divided, or, what is better, a portion of it removed. The infra-orbital 

 nerve has !>een divided at its exit by an incision on the cheek ; or the floor of the orbit has been 

 exposed, the infra-orbital canal opened up, and the anterior part of the nerve resected ; or the 

 whole nerve, together with Meek el's ganglion as far back as the foramen rotundum, has been 

 removed. This latter operation, though undoubtedly a severe proceeding, appears to have been 

 followed by the best results. The operation is performed as follows : The superior maxillary 

 bone is first exposed by a T-shaped incision, one limb passing along the lower margin of the orbit, 

 the other from the centre of this vertically down the cheek to the angle of the mouth. The 

 nerve is then found, divided, and a piece of silk tied to it as a guide. A small trephine (one- 

 half inch I is then applied to the bone below, but including, the infra-orbital foramen, and the 

 antrum opened. The trephine is now applied to the posterior wall of the antrum, and the 

 spheno-maxillary fossa exposed. The infra-orbital canal is now opened up from below by fine 

 cutting-pliers or a chisel, and the nerve drawn down into the trephine hole, it being held on the 

 stretch by means of the piece of silk ; it is severed with fine curved scissors as near the foramen 

 rotundum as possible, any branches coming off from the ganglion being also divided. 1 The 

 inferior dental nerve has been divided at its exit from the foramen by an incision made through 

 the mucous membrane where it is reflected from the alveolar process on to the lower lip ; or a 

 portion of the nerve has been resected by an incision on the cheek through the Masseter muscle, 

 exposing the outer surface of the ramus of the jaw. A trephine was then applied over the 

 position of the inferior dental foramen and the outer table removed, so as to expose the inferior 

 dental canal. The nerve was dissected out of the portion of the canal exposed, and, having been 

 divided after its exit from the mental foramen, it was by traction on the end exposed in the 

 trephine hole, drawn out entire, and cut off as high up as possible. 1 The inferior dental nerve 

 has also been divided by an incision within the mouth, the bony point guarding the inferior 

 dental foramen forming the guide to the nerve. The buccal nerve may be divided by an incision 

 through the mucous membrane of the mouth and the Buccinator just in front of the anterior 

 border of the ramus of the lower jaw (Stiinson). 



The lingual (gustatory nerve is occasionally divided with the view of relieving the pain in 

 cancerous disease of the tongue. This may be done in that part of its course where it lies below 

 and behind the last molar tooth. If a line is drawn from the middle of the crown of the last 

 molar tooth to the angle of the jaw. it will cross the nerve, which lies about half an inch behind 

 the tooth, parallel to the bulging alveolar ridge on the inner side of the bod}' of the bone. If 

 the knife is entered three-quarters of an inch behind and below the last molar tooth and carried 



1 Carnochan, Amer. Journ. Med. Scienfe, 1858, p. 136. 



2 Means, Tran#. Amer. Surg. Assoc., vol. ii. p. 469. 



