1376 SUKFACE AND SUKGICAL ANATOMY. 



as the tuberculum articulare. When the mouth is opened widely the condyle of 

 the mandible travels forwards and can be distinctly felt immediately below 

 the tubercle. To avoid entering the mandibular joint the needle is intro- 

 duced through the skin immediately below the zygoma, a little in front of the 

 eminence. It is pushed medially and slightly backwards through the sigmoid 

 notch of the mandible, and thence through, or immediately above, the external 

 pterygoid muscle, into the nerve. Symington points out that "the chief dangers 

 connected with this operation are dependent upon the needle being passed in too 

 far. Thus, if it be directed straight inwards beyond the depth of the nerve (4 cm.) 

 it would penetrate the tensor veli palatini and the auditory tube and open on the 

 lateral wall of the naso-pharynx ; or, if directed somewhat upwards, it might pass 

 through the foramen ovale, and even reach the cavernous sinus and the internal 

 carotid artery, as the medial boundary of the foramen slopes upwards and inwards." 



The facial nerve, after emerging -from the stylo-mastoid foramen, is embedded 

 in the parotid gland, where it is superficial to the external carotid artery; the 

 nerve can be rolled under the finger as it crosses the posterior border of the 

 ramus of the jaw^at the level of the lower margin of the tragus; incisions con- 

 tinued along the ramus above this point should be only skin deep if the nerve is 

 to be avoided. To expose the trunk of the nerve an incision is made from the 

 anterior border of the mastoid process to the angle of the mandible. Incisions 

 upon the cheek should, whenever possible, be planned so as to run parallel with the 

 branches of the nerve ; these radiate from the inferior end of the tragus. The 

 nerve may be paralysed by wounds of the cheek and by malignant tumours of the 

 parotid, as also by intra-cranial and middle-ear lesions. 



The parotid gland is surrounded by a fascial envelope, the strongest portion of 

 which is continued from the deep cervical fascia over its superficial aspect to 

 become attached to the zygoma (Fig. 1085) ; hence abscesses in the parotid tend 

 to burrow deeply towards the pterygo-palatine fossa and the superior part of the 

 pharynx (Fig. 1085) ; the pus should therefore be evacuated by Hilton's method, 

 through an early incision over the angle of the mandible. A study of the relations 

 of the gland explains the surgical difficulties which attend its complete removal. 



The parotid duct can be rolled beneath the finger as it crosses the masseter, 

 rather less than a finger's breadth below the zygoma. After winding round the 

 anterior border of the muscle it soon pierces the buccinator, and opens into the 

 mouth opposite to the second molar tooth of the maxilla. The duct corresponds 

 to the intermediate third of a line drawn from the inferior margin of the concha 

 to a point midway between the ala nasi and the margin of the upper lip. 



Superficial to the parotid and a little in front of the tragus is the pre-auricular 

 lymph gland, which is frequently found to be inflamed in children suffering from 

 eczematous conditions of the eyelids, face, scalp, and external ear. In opening 

 an abscess connected with this gland care must be taken to make the incision as 

 low down as possible, so as to avoid the parotid duct. 



The deep parotid lymph glands which lie partly in the substance of, and partly 

 deep to, the inferior part of the parotid, form the highest group of the medial superior 

 deep cervical lymph glands. They are especially liable to become infected secondary 

 to tuberculous disease of the middle ear and to malignant affections about the root 

 of the tongue, the fauces, and the naso-pharynx. In removing them it is generally 

 impossible to avoid dividing the cervical branch of the facial nerve, which pierces 

 the cervical fascia immediately below and behind the angle of the mandible. 

 This nerve supplies the platysma and the depressor labii inferioris muscles, so 

 that its division gives rise to inability to depress the lower lip on the affected side. 

 At the same operation some trouble may be caused by bleeding from the posterior 

 facial vein and its divisions, which traverse the substance of the gland. 



Eyelids. The skin of the eyelids, more especially of the upper, is very thin and 

 connected with the orbicularis oculi muscle by delicate and lax subcutaneous tissue 

 destitute of fat ; hence the marked swelling which occurs in a " black eye " and in 

 oedema of the lids. Along the anterior edge of the free margins of the lids are the 

 eyelashes and the orifices of the sebaceous glands, suppurative inflammation of 

 which gives rise to a " stye " ; along the sharp posterior edge of the free margins 



