262 HEAD AND NECK 



the root of the styloid process to the stylo-mastoid foramen and secure the 

 branch which springs from it to supply the posterior belly of the digastric 

 and the stylo-hyoid muscles, and the posterior auricular branch. As the trunk 

 of the nerve is being cleaned the posterior auricular branch of the external 

 carotid artery will probably be exposed, passing upwards and posteriorly 

 along the upper border of the posterior belly of the digastric to the back of 

 the external meatus, and crossing either superficial or deep to the nerve. 

 Next, remove the deeper parts of the gland and expose 4 the posterior facial 

 vein, descending towards the angle of the mandible. It receives the trans- 

 verse facial and the internal maxillary veins, and it gives off the commence- 

 ment of the external jugular vein ; 'and then it passes out of the lower end of 

 the gland and unites with the anterior facial vein to form the common facial 

 vein. Deep to the veins will be found the upper end of the external 

 carotid artery dividing into its superficial temporal and internal maxillary 

 branches ; and the transverse facial and middle temporal offsets of the 

 superficial temporal will also be displayed. 



When the remains of the deeper part of the gland have been removed, 

 the styloid process with the origin of the stylo-hyoid muscle, and the 

 posterior belly of the digastric will be exposed ; and the internal jugular vein 

 and the internal and external carotid arteries will be seen disappearing 

 under cover of the digastric. If the occipital artery lies at its lower level, 

 it also will be noted as it runs upwards and posteriorly, along the lower 

 border of the digastric, crossing superficial to the two large vessels, and 

 to the accessory nerve, which emerges from under cover of the digastric and 

 passes downwards and posteriorly across the internal jugular vein. 



The dissector should now obtain a gland which has been 

 removed uninjured from the parotid space, or a cast of a 

 gland, and proceed to study the relations of the upper end 

 and the postero-medial and antero-medial surfaces. 



The upper extremity presents a deep concavity which is 

 usually separable into a larger lateral part which lies in 

 contact with the cartilaginous part of the external meatus, 

 and a smaller medial part which touches the bony wall of the 

 meatus (Fig. 109). The anterior boundary of the upper 

 end forms a sharp ridge, which lies in the narrow interval 

 between the capsule of the temporo-mandibular articulation 

 and the front of the external meatus. 



^\\& postero-medial surface is marked by a series of depres- 

 sions which correspond with the structures in the postero- 

 medial boundary of the parotid space. Above is a shallow 

 depression corresponding with the anterior border of the 

 mastoid process, and below the latter a groove caused by the 

 anterior border of the sterno-mastoid. More medially is a 

 shallow depression due to the posterior belly of the digastric 

 and the stylo-hyoid, and, still more medially and at a higher 

 level, a sulcus which corresponds with the position of the 

 styloid process. Below the level of the digastric groove the 

 postero-medial surface covers portions of the internal jugular 



