176 THE HEAD AND NECK 



Branches of the great auricular nerve ramify over the surface 

 of the sheath, and the auriculo-temporal nerve pierces it just 

 below the zygomatic process of the temporal bone. Any acute 

 or rapidly growing swelling within the sheath will press on these 

 nerves and give rise to pain, which is referred to the areas of 

 their distribution. In acute parotitis examples of this pain are 

 afforded during the activity of the gland at meal-times. 



The facial nerve, the external carotid artery, and the posterior 

 facial (temporo-maxillary) vein are all more or less embedded 

 in the substance of the gland. The nerve traverses the gland 

 and crosses the vessels superficially. 



The Parotid Duct lies one finger's breadth below the zygo- 

 matic arch, and, when the teeth are clenched, it may be rolled 

 up and down against the tense masseter. It emerges from the 

 forepart of the gland, and runs forwards on the masseter to its 

 anterior border. It then passes medially, piercing the buccin- 

 ator to reach the mucous membrane of the cheek. Opposite 

 the second upper molar tooth the parotid duct opens into the 

 mouth. Septic infection may travel backwards from the mouth 

 along the duct and involve the gland itself. 



Calculi lodged in the distal portion of the duct may be 

 removed by slitting up the duct from its opening within the 

 mouth. A similar route is adopted for opening abscesses in 

 connection with the buccinator lymph glands. The incision is 

 made horizontally through the mucous membrane to one side 

 of the opening of the parotid duct, and both the mucous mem- 

 brane and the buccinator are cut parallel to the course of the 

 duct. 



The Buccinator arises from the outer alveolar margins of 

 the maxilla and mandible in the region of the molar teeth, and 

 its posterior border is attached to the pterygo-mandibular 

 raphe, which is a fibrous band extending from the hamulus of 

 the medial pterygoid lamina (plate) to the posterior end of the 

 mylo-hyoid line of the mandible. Its fibres run horizontally 

 forwards, and fuse with the orbicularis oris at the angle of the 

 mouth. Like the muscles of facial expression, it is supplied by 

 the facial nerve. It forms the muscular stratum of the cheek, 

 and when it is paralysed portions of food become retained 

 between the cheek and the gums on the affected side. 



The lymph glands of the parotid region are divisible into 

 two groups; one, the anterior auricular (pre-auricular) , lies super- 

 ficial to the sheath, while the other, the group of parotid lymph 



