THE COMMON CAEOTID ARTEBIES. 587 



commence from the third section of the artery : two inferior, the buccal and 

 palatine ; and two upper, the superior dental and the nasal. 



1. INFERIOR DENTAL ARTERY (Fig. 286, 28). This vessel, also named 

 the maxillo-dental artery, is detached at a right angle from about the 1 middle 

 of the first curvature described by the internal maxillary. It travels 

 forward and downward between the two pterygoid muscles, afterwards 

 between the internal one and the maxillary bone, entering with the inferior 

 maxillary nerve into the dental canal, through the whole extent of which it 

 passes. Arrived at the mental foramen, it separates into two branches : a 

 deep one, which continues the interosseous course of the vessel, to be 

 distributed to the roots of the tusk or tush, and the three adjoining incisor 

 teeth; the other superficial, generally very slender and even capillary, 

 issuing by the mental foramen with the terminal branches of the maxillary 

 nerve, and anastomosing with the inferior coronary artery. 



Before penetrating the maxilla, this artery furnishes divisions to the 

 internal pterygoid and mylo-hyoid muscles. 



In the interior of the maxillo-dental canal, it gives off diploic branches 

 as well as twigs, destined to the roots of the molar teeth and the alveolar 

 membrane. 



2. PTERYGOID ARTERIES (Fig. 286, 29). It may be said, in a 

 general manner, that the two pterygoid muscles borrow their arteries from 

 all the vessels passing near them, though there are two, and sometimes three, 

 branches more especially intended for them. These branches, or, properly 

 speaking, pterygoid arteries, arise from the middle of the second curvature of 

 the internal maxillary, either at an acute or right angle, and enter the 

 pterygoid muscles, after a short course forward and downward on the 

 external tensor palati muscle ; this and its fellow, the internal muscle, also 

 receiving some branches. 



3. TYMPANIC ARTERY (Fig. 286, 30). A very thin and small, but constant 

 artery, gliding along the surface of the guttural pouch, accompanying 

 the tympano-lingual nerve, and penetrating the tympanic cavity by a foramen 

 situated at the base of the styloid process of the temporal bone (the fissura 

 Glaseri). It throws off ramuscules to the wall of the guttural pouch 

 and the trigeminal nerve ; these often arise directly from the trunk of the 

 internal maxillary artery, besides the tympanic branch. 



4. SPHENO-SPINOUS OR GREAT MENINGEAL ARTERY (Fig. 286, 31). 

 Commencing at an obtuse angle, opposite the pterygoideal vessels, this 

 artery lies against the sphenoid bone, near the temporal insertion of 

 the tensor palati muscles, is directed backwards and upwards, enters the 

 cranium by the anterior lacerated foramen, outside the inferior maxillary 

 nerve, passes beneath the dura mater, and soon after engages itself in 

 a particular foramen in the parieto-temporal canal, where it anastomoses by 

 inosculation with the mastoid artery. 



Before penetrating this canal, the spheno-spinous artery gives off 

 a meningeal branch, whose ramifications, destined to the dura mater, stand 

 in relief on that membrane, and creep along in the small grooves channeled 

 on the inner surface of the cranium. 



The volume of this vessel is subject to the greatest variations, and 

 is always in an inverse proportion to that of the mastoid artery. 



5. DEEP POSTERIOR TEMPORAL ARTERY (Fig. 286, 32). This arises at 

 a right angle, immediately before the entrance of the internal maxillary 

 artery into the subsphenoidal canal. Then it ascends on the temporal bone, 

 in the temporal muscle, passing in front of the temporo maxillary articula- 



