When the posterior auris gets to the front of tile mastoid process it divides into two branches, one of which is anterior and the other pos terior; the former spreads its branches over all parts of the internal surface of the ear ; the latter ascends in front of the mastoid process, passes under the posterior auris muscle, and divides into many branches, which are distri buted to the occipito-frontalis and temporal muscles, integuments, Scc.
These branches anastomose with the temporal and occipital arteries.
While traversing the parotid gland the ex ternal carotid gives several small branches to the masseter and pterygoid muscles, to the substance of the gland itself, and a few to the front of the external ear ; occasionally it gives origin to the transversalis faciei in this course.
Behind the neck of the condyle of the lower jaw the external carotid divides into its two superior and terminal branches, the temporal and internal maxillary.
1. Temporal artery, ( a. temporalis.) The temporal artery ascends at first a little obliquely outwards between the ramus of the jaw and the tube of the ear, covered by the parotid gland ; crossing the zygoma at its posterior part, and passing under the anterior auris muscle, it mounts up over the temporal apo neurosis, and becomes subcutaneous for the remainder of its course.
Immediately after its origin the temporal gives off anteriorly a very considerable branch, which is called the transversalisfaciei : this artery sometimes arises from the trunk of the external carotid ; it passes forvvard over the neck of the condyle of the lower jaw, and, crossing the masseter muscle, runs superior to the duct of Steno, which it accompanies across the face; it anastomoses with the labial, buccal, and infra-orbital arteries. The branches which the transversalis faciei usually gives off are distributed to the parotid gland and its duct, the masseter, zygomatic, and orbicularis pal pebralum muscles, and the integuments. I have seen an instance in which this artery arose from the external carotid opposite the angle of the jaw, beneath which it passed forwards, and joined the labial at the anterior edge of the masseter muscle.
When the temporal artery has arrived at the zygoma, it gives a branch called middle tem poral, which pierces the temporal aponeurosis, and ascends in the substance of the temporal muscle, to which it is distributed, and which anastomoses with the deep temporal arteries.
Having given off a few small branches to the parotid gland, integuments, and external ear, the temporal artery ascends on the temporal aponeurosis, and divides into two branches, the anterior and posterior. The anterior branch ascends in a serpentine course towards the forehead, and sends off many branches, which are distributed to the occipito-frontalis, the orbicularis palpebrarum, and integuments, and which anastomose with the superciliary and frontal branches of the ophthalmic and with the opposite temporal. The posterior branch passes upwards and backwards in a tortuous course, and supplies the integuments, tem poral aponenrosis, pericranium, &c. These branches anastomose with the anterior branch, with the opposite temporal, the occipital, and posterior auris.
2. The internal maxillary artery, (a. nzaxil lapis interna,) is larger than the preceding; im mediately after its origin it passes downwards and inwards under the neck of the condyle of the lower jaw; it then mounts forwards and in wards between the temporal and external ptery goid muscles, and usually passing between the two origins of the latter, it enters the pterygo maxillary fossa, where it ascends as high as the level of the inferior wall of the orbit, oppo site which it takes a horizontal direction. At this place it divides into numerous branches, which are distributed on one side inwards to wards the nose, and on the other side to the external part of the face.
The branches of the internal maxillary are, a. the middle meningeal, b. the inferior dental, c. the posterior deep temporal, d. the masseteric, e. pterygoid branches, j: the buccal, g. the an terior deep temporal, h. the alveolar, i. the infra-orbital, l. the superior palatine, m. the vidian, n. the pterygo-palatine, and o. the spheno-palatine: in addition to these the in ternal maxillary artery gives several branches to the cellular tissue and other parts surrounding it.