498 THE BLOOD-VASCULAR SYSTEM. 



Surgical Anatomy. The middle meningeal is an artery of considerable surgical import- 

 ance, as it may be injured in fractures of the temporal region of the skull, and the injury may 

 be followed by considerable haemorrhage between the bone and dura mater, which may cause 

 compression of the brain and require the operation of trephining for its relief. This artery 

 crosses the anterior inferior angle of the parietal bone at a point 1 inches behind the external 

 angular process of the frontal bone, and 1 1 inches above the zygoma. From this point the ante- 

 rior branch passes upward and slightly backward to the sagittal suture, lying about inch to 

 f inch behind the coronal suture. The posterior branch passes upward and backward over the 

 squamous portion of the temporal bone. In order to expose the artery as it lies in the canal in 

 the parietal bone, a semilunar incision, with its convexity upward, should be made, commencing 

 an inch behind the external angular process, and carried backward for 2 inches. The structures 

 cut through are : (1) skin ; (2) superficial fascia, with branches of the superficial temporal vessels 

 and nerves; (3) the fascia continued down from the aponeurosis of the Occipito-frontalis ; (4) 

 the two layers of the temporal fascia; (5) the temporal muscle ; (6) the deep temporal vessels ; 

 (7) the pericranium; and (8) the bone. 



The small meningeal is sometimes derived from the preceding. It enters the 

 skull through the foramen ovale, and supplies the Gasserian ganglion and dura 

 mater. 



The inferior dental descends with the inferior dental nerve to the foramen on 

 the inner side of the ramus of the jaw. It runs along the dental canal in the sub- 

 stance of the bone, accompanied by the nerve, and opposite the first bicuspid tooth 

 divides into two branches, incisor and mental ; the former is continued forward 

 beneath the incisor teeth as far as the symphysis, where it anastomoses with the 

 artery of the opposite side ; the mental branch escapes with the nerve at the mental 

 foramen, supplies the structures composing the chin, and anastomoses with the sub- 

 mental inferior labial and inferior coronary arteries. Near its origin the inferior 

 dental artery gives off a lingual branch, which descends with the lingual (gustatory) 

 nerve and supplies the mucous membrane of the mouth. As the inferior dental 

 artery enters the foramen it gives off a mylo-hyoid branch, which runs in the mylo- 

 hyoid groove, r.nd ramifies on the under surface of the Mylo-hyoid muscle. The 

 dental and incisor arteries during their course through the substance of the bone 

 give off a few twigs which are lost in the cancellous tissue, and a series of branches 

 which correspond in number to the roots of the teeth : these enter the minute 

 apertures at the extremities of the fangs and supply the pulp of the teeth. 



BRANCHES OF THE SECOND OR PTERYGOID PORTION. 



Deep Temporal. Masseteric. 



Pterygoid. Buccal. 



These branches are distributed, as their names imply, to the muscles in the 

 maxillary region. 



The deep temporal branches, two in number, anterior and posterior, each occupy 

 that part of the temporal fossa indicated by its name. Ascending between the 

 Temporal muscle and pericranium, they supply that muscle and anastomose with 

 the middle temporal artery, the anterior branch communicating with the lachrymal 

 through small branches which perforate the malar bone and great wing of the 

 sphenoid. 



The pterygoid branches, irregular in their number and origin, supply the 

 Pterygoid muscles. 



The masseteric is a small branch which passes outward, above the sigmoid 

 notch of the lower jaw,'to the deep surface of the Masseter. It supplies that 

 muscle, and anastomoses with the masseteric branches of the facial and with the 

 transverse facial artery. 



The buccal is a small branch which runs obliquely forward between the Internal 

 pterygoid and the ramus of the jaw, to the outer surface of the Buccinator, to 

 which i-t is distributed, anastomosing with branches of the facial artery. 



