262 BLOOD-VESSELS OF THE TEETH. 



face at the infra orbital foramen, anastomosing with the 

 facial and transverse facial arteries. Just before it emerges, 

 it sends down, in the anterior dental canal, a branch to 

 supply the incisors and cuspidati, and also the lining 

 membrane of the antrum. 



The inferior dental arises from the internal maxillary 

 behind the neck of the lower jaw, descends to the poste- 

 rior mental foramen, which it enters along with the dental 

 nerve; thence it passes along the canal beneath the roots 

 of the teeth, sending up into each, in its course, small 

 twigs which supply the molars. When opposite the bicus- 

 pid, it divides into two branches the one being the con- 

 tinued trunk which proceeds forwards to the symphysis, 

 supplying the anterior teeth, while the second branch 

 passes out at the anterior mental foramen, upon the side 

 and front of the chin, anastomosing with branches of the 

 facial artery. 



The internal maxillary vein, made up of the veins corre- 

 sponding to the several branches of the internal maxillary 

 artery, returns the blood of the artery, and passing behind 

 the neck of the jaw, unites in the substance of the parotid 

 with the temporal vein the junction of the two mainly 

 forming the external jugular, which passes superficially 

 down the neck, to terminate in the subclavian vein. 



THE NERVES OF THE TEETH. (Fig. *74.) 



The nerves supplying the teeth come from the fifth pair, 

 and are nerves of sensation. The fifth nerve can be traced 

 to the spinal cord, having its roots in the anterior and pos- 

 terior columns ; hence it is called the cranial-spinal nerve. 

 Being a spinal nerve, it has on its posterior root a ganglion, 

 and the junction of the anterior and posterior roots consti- 

 tutes properly the fifth nerve. It is seen to emerge at the 

 .side of the Pons-varolii on the anterior part of the cms- 

 cerebelli. At this point it is composed of from 80 to 100 

 filaments, which pass forward in a canal of the dura-mater 

 upon the anterior surface of the petrous bone, in a depres- 

 sion of which it expands into a ganglion called the Gasse- 



