742 HUMAN ANATOMY. 



emergence from the posterior palatine foramen, divides into an anterior and a posterior branch. 

 The former passes forward beneath the mucous membrane of the hard palate, which it supplies, 

 and at the anterior palatine foramen anastomoses with the spheno-palatine artery ; the latter 

 passes backward to supply the .soft palate and the tonsil, anastomosing with the ascending 

 palatine branch of the facial. 



(«) The Vidian artery (a. canalis pterygo'idei ) is a small branch which passes backward along 

 the Vidian nerve through the \'idian canal, and sends branches to the roof of the pharynx and 

 to the Eustachian tube. 



(o) The pterygo-palatine artery (a. palatina major) is also a somewhat slender branch. It 

 passes backward through the pterygo-palatine foramen along with the pharyngeal nerve from 

 the spheno-palatine ganglion, and supplies the roof of the pharyn.x, the Eustachian tube, and 

 the mucous membrane lining the sphenoidal cells. 



(/) The spheno-palatine artery (a. sphenopalatina) is the terminal branch of the internal 

 maxillary. It passes into the nasal ca\'ity through the spheno-palatine foramen along with the 

 spheno-palatine nerve from the spheno-palatine ganglion. Shortly after traversing the foramen 

 it divides into an internal and an external branch. The iJiternal branch, sometimes termed the 

 naso-palatine, passes transversely across the roof of the nasal cavity to reach the septum, upon 

 which it passes downward and forward, giving off numerous branches which anastomose to form 

 a rich net-work beneath the mucous membrane of the septum. It finally reaches the anterior 

 palatine foramen, where it anastomoses with the anterior branch of the descending palatine. 

 Throughout its course it is accompanied by the naso-palatine nerve. The external branch 

 ramifies downward and forward over the lateral wall of the nasal fossa, forming a rich plexus 

 beneath the mucous membrane lining the meatuses and the turbinate bones. 



It will be observed that all the branches arising from the first and third portions of the 

 internal maxillary artery tra\'erse bony canals or foramina, while those of the second portion 

 do not, but are distributed directly to muscles. 



Anastomoses. — The communications of the internal maxillary artery are with 

 the branches of the artery of the opposite side, with other branches of the artery of the 

 same side, with other branches of the external carotid, and with brjmches of the 

 internal carotid. The most abundant anastomoses with the artery of the opposite 

 side are made through the branches of the middle meningeal; the ah-eolar branch 

 anastomoses wdth the dental branches of the infraorbital of the same side and with 

 the buccal artery, and the anterior branch of the descending palatine makes a large 

 anastomosis with the naso-palatine branch of the spheno-palatine at the anterior 

 palatine foramen. The other branches of the external carotid with which anastomoses 

 are made are the facial, the temporal, and the posterior auricular; the facial com- 

 municates by means of its submental and inferior labial branches with the mental 

 branch of the inferior dental, by its superior coronary and angular branches with the 

 terminal branches of the infraorbital, by its superior coronary with branches of the 

 naso-palatine, and by its ascending palatine with branches of the descending palatine. 

 The deep temporal arteries anastomose with branches of the superficial temporal and 

 the infraorbital with the transverse facial branch of the same artery; while the 

 posterior auricular communicates by means of its stylo-mastoid branch with the 

 tympanic branch and with the petrosal branch of the middle meningeal. 



Of the anastomoses with the internal carotid arteries the most important are 

 those between the orbital branch of the middle meningeal and the lachrymal artery, 

 between the terminal branches of the infraorbital* and the terminal branches of the 

 ophthalmic, and between the spheno-palatine branches and the ethmoidal arteries. 



Variations. — In the early stages of development the main portion of the internal maxillary 

 is represented by a stem which arises from the internal carotid (Tandler). This is known ^s 

 the a. stapedia (Fig. 694, Ast), since it traverses the middle ear, passing through the foramen 

 of the stapes (.y/); it makes its exit from the middle ear by the Glaserian fissure and divides into 

 two stems, one of which [Rs') passes through the foramen spinosum {fsp) and is distributed to 

 the supraorbital region, while the other divides into two branches which, from their distribution, 

 are termed the infraorbital (/?/) and the mandibular (inferior dental) {Rm). A branch (Ras) 

 arises later from the external carotid which anastomoses with the lower stem where it divides 

 into the two branches just mentioned, and the main stem of the stapedius disappears, except 

 in its distal portion, which persists as the tympanic liranch of the internal maxillary, which fre- 

 quently arises in the adult from the middle meningeal instead of directly from the internal max- 

 illarv. By these changes, as may be seen from the accompanying diagrams, the adult internal 

 maxillary is formed, the supraorbital brjjnch becoming the middle meningeal { Mm) and the 

 mandibular branch the inferior dental, while the infraorbital branch {Rt) becomes the mam • 

 stem of the artery from which t'le remaining branches gradually develop. 



