1134 SPLANCHNOLOGY 



while the outer lip extends for some distance over the superficial surface of the 

 Masseter; a small portion of this lip immediately below the zygomatic arch is 

 usually detached, and is named the accessory part (soda parotidis] of the gland. 



The posterior surface is grooved longitudinally and abuts against the external 

 acoustic meatus, the mastoid process, and the anterior border of the Sterno- 

 cleidomastoideus. 



The superficial surface, slightly lobulated, is covered by the integument, the 

 superficial fascia containing the facial branches of the great auricular nerve and 

 some small lymph glands, and the fascia which forms the capsule of the gland. 



The deep surface extends inw r ard by means of two processes, one of which lies 

 on the Digastricus, styloid process, and the styloid group of muscles, and projects 

 under the mastoid process and Sternocleidomastoideus; the other is situated in 

 front of the styloid process, and sometimes passes into the posterior part of the 

 mandibular fossa behind the temporomandibular joint. The deep surface is in 

 contact with the internal and external carotid arteries, the internal jugular vein, 

 and the vagus and glossopharyngeal nerves. 



The gland is separated from the pharyngeal wall by some loose connective 

 tissue. 



Structures within the Gland. The external carotid artery lies at first on the deep 

 surface, and then in the substance of the gland. The artery gives off its posterior 

 auricular branch which emerges from the gland behind; it then divides into its 

 terminal branches, the internal maxillary and superficial temporal; the former runs 

 forward deep to the neck of the mandible; the latter runs upward across the zygo- 

 matic arch and gives off its transverse facial branch which emerges from the front 

 of the gland. Superficial to the arteries are the superficial temporal and internal 

 maxillary veins, uniting to form the posterior facial vein ; in the lower part of the 

 gland this vein splits into anterior and posterior divisions. The anterior division 

 emerges from the gland and unites with the anterior facial to form the common 

 facial vein; the posterior unites in the gland with the posterior auricular to form 

 the external jugular vein. On a still more superficial plane is the facial nerve, the 

 branches of which emerge from the borders of the gland. Branches of the great 

 auricular nerve pierce the gland to join the facial, while the auriculotemporal nerve 

 issues from the upper part of the gland. 



The parotid duct (ductus parotideus; Stensen's duct} is about 7 cm. long. It 

 begins by numerous branches from the anterior part of the gland, crosses the Masse- 

 tejr, and at the anterior border of this muscle turns inward nearly at a right angle, 

 passes through the corpus adiposum of the cheek and pierces the Buccinator; it 

 then runs for a short distance obliquely forward between the Buccinator and mucous 

 membrane of the mouth, and opens upon the oral surface of the cheek by a small 

 orifice, opposite the second upper molar tooth. While crossing the Masseter, 

 it receives the duct of the accessory portion; in this position it lies between the 

 branches of the facial nerve; the accessory part of the gland and the transverse 

 facial artery are above it. 



Structure. The parotid duct is dense, its wall being of considerable thickness; its canal is 

 about the size of a crow-quill, but at its orifice on the oral surface of the cheek its lumen is 

 greatly reduced in size. It consists of a thick external fibrous coat which contains contractile 

 fibers, and of an internal or mucous coat lined with short columnar epithelium. 



Vessels and Nerves. The arteries supplying the parotid gland are derived from the external 

 carotid, and from the branches given off by that vessel in or near its substance. The veins 

 empty themselves into the external jugular, through some of its tributaries. The lymphatics 

 end in the superficial and deep cervical lymph glands, passing in their course through two or 

 three glands, placed on the surface and in the substance of the parotid. The nerves are derived 

 from the plexus of the sympathetic on the external carotid artery, the facial, the auriculotem- 

 poral, and the great auricular nerves. It is probable that the branch from the auriculotemporal 

 nerve is derived from the glossopharyngeal through the otic ganglion. At all events, in some of 

 the lower animals this has been proved experimentally to be the case. 



