a. Me middle meningeal artery ( a.meningea media, spinosa) arises from the superior part of the artery and passes directly upwards on the inside of the external pterygoid muscle, to which, to the superior constrictor of the pharynx and muscles of the velum palati it sends branches, and passing between the tensor palati muscle and internal lateral ligament of the temporo-maxillary articulation, enters the cranium through the foramen spinale of the sphenoid bone, and immediately gives off some small branches, which pass through the hiatus Fallopii to the cavity of the tympanum, where they anastomose with the stylo-mastoid artery; other branches pass forwards towards the orbit into which some of them occasionally enter by the foramen lacerum. The meningeal artery then divides into two branches, an anterior and a posterior; the anterior, which is the larger, might be considered as the continued trunk; it mounts forwards towards the anterior inferior angle of the parietal bone, where it is lodged in a groove, and sometimes in a canal in the sub stance of that bone. This branch at first gives twigs to the foramen lacerum, which anastomose with the lachrymal ; after which it mounts on the parietal bone, principally following the course of the coronal suture, sending its bran ches upwards and backwards between the dura mater arid the inner surface of the parietal bone. The posterior branch passes backwards in a curved direction on the inner surface of the squamous portion of the temporal bone, and advancing- towards the inferior border of the parietal bone, is expended on the posterior and lateral part of the dura mater. The branches of the middle meningeal artery spread over the external surface of the dura mater, and occupy the grooves which are disposed in an arbores cent form on the internal surface of the parietal bone. The middle meningeal artery ariasto moses with that of the opposite side and with the other arteries of the dura mater.
b. The inferior maxillary or inferior dental artery sometimes coming from the middle me ningeal, descends to the posterior dental hole by which it enters the dental canal, passing be tween the inner surface of the ramus of the jaw and the outer surfaces of the internal pterygoid muscle and the internal lateral ligament of the temporo-maxillary articulation, to which it gives small twigs : before it enters the dental hole, it gives off a small branch, which passing down wards and forwards in a groove on the inside of the lower jaw, is distributed to the mylo hyoid muscle and mucous membrane of the mouth. In the dental canal this artery passes forwards beneath the alveoli of the molar teeth, sending upwards in its course several branches which penetrate into the alveoli, and enter the cavities of the teeth by the holes in their roots ; having arrived opposite the mental hole, it sends a branch which passes onwards beneath the alveoli of the canine and incisor teeth, to which it is distributed ; while the continuation of the artery coming out through the mental hole is distributed to the muscles of the lower lip, where it anastomoses with the labial.
c. The posterior deep temporal artery arises after the dental ; it passes upwards between the temporal and external pterygoid muscles, and sinking into the substance of the former, divides into a great number of branches, which spread over the squamous portion of the temporal bone, and are distributed to the temporal mus cle and pericranium. This artery anastomoses with the anterior deep temporal, the middle, and the superficial temporal.
d. The masseteric is a small branch often arising from the posterior deep temporal ; it passes outwards between the posterior border of the temporal muscle and the condyle of the lower jaw, and enters the masseter muscle, where it anastomoses with the transversalis faciei.
e. The pterygoid arteries are irregular as to number, size, and origin ; they either come from the trunk of the internal maxillary or the posterior deep temporal, and are distributed to the pterygoid muscles.
f. The buccal artery does not always arise from the internal maxillary itself; it sometimes comes from the anterior deep temporal, the alveolar, or infra-orbital. It passes downwards and forwards between the internal pterygoid muscle and ramus of the lower jaw, and ad vances over the surface of the buccinator mus cle, to which it gives branches, as well as to the zygomatic and other muscles of the lip : it anastomoses with the labial, infra-orbital, and transversalis faciei.
g. The anterior deep temporal arises from the internal maxillary, near the outer wall of the temporal fossa beneath the temporal mus cle, to which it is distributed ; some of its branches enter the orbit through the malar bone, and spread over the lachrymal gland, communicating with the lachrymal artery.
h. The alveolar artery descends forwards over the superior maxillary bone, very tortuous in its course; it gives two or three twigs, which pass into the inferior and posterior dental fora mina to be distributed to the lining membrane of the antrum maxillare and the molar teeth; the other branches of the alveolar artery are distributed to the gums, to the buccinator, to the periosteum of the superior maxillary bone, and to the cellular substance of the cheek : they communicate with the infra-orbital, labial and buccal.
i. The infra-orbital artery arises from the internal maxillary at the superior part of the pterygo-maxillary space ; it enters the infra orbital canal, through which it passes forwards and inwards, sending branches into the orbit and maxillary sinus; passing out by the infra orbital hole it comes forward on the face behind the levator labii superioris, and termi nates in a number of branches, which pass into the muscles of the upper lip, and anastomose with the labial, alveolar, buccal, and nasal branch of the ophthalmic.
The remaining branches of the internal max illary are given off in the pterygo-maxillary space; of these the first is 1. The superior palatine descends behind the tuberosity of the superior maxillary bone in the palato-maxillary canal : it usually gives off two branches, which descend through holes in the pterygoid process of the' palate bone, and are distributed to the soft palate ; while the trunk of the superior palatine passing out of the posterior palatine hole, directs itself for wards and inwards in a groove on the surface of the hard palate, and divides into numerous branches, which are distributed to the mucous membrane and glands of the palate, to the gums, and to the superior maxillary bone ; one of these branches sometimes passes up through the foramen incisivum to the nasal fossT.
m. The vidian artery is an insignificant branch which traverses the vidian canal from before backwards, and coming out of its poste rior opening is distributed to the Eustachian tube and the roof of the pharynx: it anasto moses with the inferior pharyngeal.
n. The ptery go-palatine or superior pha ryngeal is a small insignificant branch, which passes through the pterygo-palatine hole, and is distributed like the former to the roof of the pharynx and Eustachian tube, sending some branches to the sphenoid bone and the mem brane lining its sinuses.
o. The .spheno-palatine artery may be con sidered the termination of the internal maxil lary ; it enters by the spheno-palatine hole into the posterior part of the nasal fossw, and divides into two principal branches ; an external and an internal; the internal branch passing across the roof of the -nasal fossa2 arrives at the septum, on which its branches are principally distri buted ; it also supplies branches to the roof of the pharynx and tile posterior ethmoidal cells; the external branch descends on the lateral wall of the nose, sending its branches over the spongy bones and into the antrum maxillare : these branches anastomose with the ethmoidal branches of the ophthalmic artery.