Arteries.—The external carotid artery passes into the lower border of the gland near its deep surface; as it ascends it becomes more superficial, and is continued upwards under the name of the supeificial temporal, which passes up between the ear and the articulation of the jaw, crosses over the zygoma, and so emerges from beneath the parotid gland and its fascia.
The internal maxillary artery passes off from the carotid at right angles. At its origin it is imbedded in the substance of the parotid, and is nearly on a level with the lower extre niity of the lobe of the ear; it bends down wards and inwards, and escapes from the pa rotid by passing between the ramus of the jaw and its internal lateral ligament.
The transversalis faciei arises from the ca rotid or from the superficial tenipoml artery at a variable distance between the angle and neck of the jaw. Its origin is imbedded in the substance of the parotid; it then goes upwards and furwards, and passes out beneath the ante rior border of the gland, lying betvveen it and the masseter muscle.
The posterior auricular artery is a small branch of uncertain origin. When regular it arises from the external carotid, above the di gastric and stylo-hyoid muscles, opposite the point of the styloid process; it is here partly concealed by the parotid gland, in the posterior part of which it is imbedded ; it then passes upwards and backwards between the ear and the mastoid process. While this artery is im bedded in the parotid it sends off a small stylo-mastoid branch, which passes upwards to enter the stylo-mastoid foramen. In ad dition to the above-mentioned arteries there are several branches variable in their number, size, and situation, which pass off from the carotid and its branches and are distributed to the substance of the parotid gland.
Veins.—The veins corresponding to the ter minal branches of the external carotid artery accompany the arteries and are consequently imbedded in the parotid gland. The temporal and internal maxillary veins unite and forin a common trunk, which lies superficial to the external carotid artery. This common trunk receives the posterior auricular and the trans verse facial veins, as well as some veins from the substance of the parotid, and so the corn mencement of the external jugular vein is formed. There is also a communicating branch which passes through the parotid gland from the internal to. the external jugular vein ; this branch may be looked upon as one of the origins, and in some cases it is the chief origin of the external jugular vein.
Nerves.—We have next to study the rela tions of the nerves which are found in the parotid region.
The nerve which lies most superficially in this region is the great auricular, some small branches of which lie superficial to the parotid fascia and are distributed to the skin of the parotid region, while other branches pierce the fascia, and pass through the parotid in a di rection fonvards and upwards to be distributed on the skin of the cheek. The nerve then sends off two branches, the superficial auri cular and the deep auricular.
The superficial auricular branch of the great auricular nerve passing vertically upwards in the dense fibrous tissue which connects the parotid with the skin, reaches the inferior part of the concha, and is distributed to the skin of the ear.
The deep auricu7ar branch passes through the substance of the parotid, to place itself in front of the mastoid process, crossing at an acute angle the auricular branch of the facial nerve, which is deeper than it, and with which it anastomoses by a branch of considerable size. The nerve then passes backwards and divides into branches which are distributed to the ex ternal ear, and to the skin over the occipital region.
The auriculo-tentporal nerve arises from the trunk of the superior maxillary by two por tions, between which passes occasionally the middle meningeal artery. It posses backwards beneath the external pterygoid muscle, and between the internal lateral ligament and neck of the jaw ; it then divides into two branches, a superficial or temporal and a deep or auri cular branch. The superficial temporal passes up between the ear and the articnlation of the jaw, crossing the root of the zygoma, and be coming superficial above the parotid gland ; it then supplies the skin of the temple and side of the head. In its course this nerve sends off one or tvvo branches which comtnunicate with the portio dura nerve; it also sends branches to the ternpero-maxillary articulation and to the external auditory meatus. The auricular branch forms a plexus behind the neck of the jaw and around the internal maxillary artery; it then divides into several branches, some of which pass through the parotid to be distributed on the external ear, while others anastomose with branches of the cervical plexus, _particularly with the great auricular nerve. One branch joins the dental nerve just before it enters the dental canal, and another passes into the tem pero-maxillary articulation.