THE FACE. 1375 



I felt to glide forwards, while the finger sinks deeply into the hollow corresponding 

 i to the mandibular fossa. The close relation of the first part of the internal maxillary 



artery to the medial aspect' of the neck of the mandible must be kept in mind in 

 | operations calling for disarticulation or excision of the condyle. The ramus of the 



mandible is sandwiched between the masseter and the pterygoid muscles, and 

 ; can be removed without opening into the mouth. Passing downwards from the 

 [condyle, one can palpate the anterior and posterior borders of the ramus and the 



angle and body of the mandible. The anterior border of the coronoid process is felt 



.in front of the upper part of the anterior border of the masseter, immediately below 

 ! the anterior part of the zygomatic arch. 



The pulsation of the external maxillary artery may be felt as the vessel crosses 

 I the inferior margin of the mandible at the anterior border of the masseter, 1J in. in 

 I front of the angle of the mandible. To map out the course of the artery upon the 

 1 face, draw a line from this point to a point J in. lateral to the angle of the mouth, 

 land thence to a point a little behind the ala nasi and along the side of the nose to 

 1 the medial angle of the orbit. The anterior facial vein lies posterior to the external 

 j maxillary artery, and takes a straighter course from the medial palpebral commissure 

 1 to the anterior inferior angle of the masseter. The vessel is devoid of valves, hence 

 'infective phlebitis and thrombosis are liable to spread along it to the cavernous 

 J sinus by way of the ophthalmic and pterygoid veins. 



A line projected downwards from the supra-orbital notch (junction of medial 

 land intermediate thirds of the supra-orbital margin) to the inferior border of the 

 j mandible opposite the interval between the two lower premolar teeth, will cross 

 Ithe infra-orbital and mental foramina, the former J in. below the infra-orbital 

 {margin, the latter midway between the superior and inferior borders of the 

 I mandible. In performing the operation of neurectomy for the relief of trigeminal 

 [neuralgia, these foramina furnish the guides to the correspondingly-named branches 

 [of the fifth nerve. It should be remembered that the nerves in question, after 

 I: emerging from their respective foramina, lie, in the first instance, beneath the 

 i facial muscles. The supra-orbital and infra-orbital nerves are not, infrequently 

 [represented each by two branches, one of which passes through an accessory 

 j foramen situated lateral to the normal opening. Neurectomy of the inferior 



alveolar nerve is performed by trephining the ramus of the mandible midway 

 I between its anterior and posterior borders, on a level with the crown of the 

 last molar tooth, the nerve being reached as it enters the inferior alveolar canal : 

 jthe lingual nerve, which lies a little anterior to the inferior alveolar, can be 

 .exposed through the same opening. 



The relations of the maxillary and mandibular divisions of the trigeminal nerve 

 j have become of increased importance to the surgeon since the introduction of the 

 J treatment of trifacial neuralgia by the injection of alcohol into these nerves 

 i immediately after their exit from the cranial cavity. According to Symington, 

 in order to reach the maxillary nerve as it lies in the pterygo-palatine fossa, 

 '.the skin should be punctured immediately below the zygomatic arch, about 4 cm. 

 an front of the anterior wall of the external acoustic meatus. The needle should 

 >be directed medially with a slight inclination upwards and backwards. After 

 i perforating the masseter and temporal muscles, the instrument enters the fatty 

 J tissue of the infra-temporal fossa, embedded in which is the internal maxillary 

 I artery and some veins. By passing the needle still more deeply, it is made to 

 [penetrate between the two heads of the external pterygoid muscle through the 

 I pterygo-maxillary fissure into the pterygo-palatine fossa. If the instrument be 

 i passed too far forwards it will strike the maxillary tuberosity ; if too far back- 

 i\ wards, the lateral pterygoid lamina. The oedema of the eyelids which not in- 

 frequently follows the operation is due to some of the fluid passing upwards into 

 I the orbit through the inferior orbital fissure. The distance from the skin to the 

 'i nerve, as it lies in the pterygo-palatine fossa, is practically 2 in. Should the 



needle, after perforating the masseter, strike the coronoid process of the mandible, 

 [the latter may be depressed by opening the mouth. 



The mandibular nerve is injected immediately beyond its exit from the 

 foramen ovale, which lies 4 cm. from the skin in the same vertical frontal plane 



