49b' THE BLOOD-VASCULAR SYSTEM. 



Surgical Anatomy. Formerly the operation of arteriotomy was performed upon this 

 vessel in cases of inflammation of the eye or brain, but now the operation is probably never 

 performed. If the student will consider the relations of the trunk of the vessel as it crosses 

 the zygomatic arch, with the surrounding structures, he will observe that it is covered by a 

 thick and dense fascia, crossed by one of the main divisions of the facial nerve and one or 

 two veins, and accompanied by the auriculo-temporal nerve. Bleeding should not be performed 

 in this situation, as much difficulty may arise from the dense fascia over the vessel preventing a 

 free flow of blood, and considerable pressure is requisite afterward to arrest the hemorrhage. 

 Again, a varicose aneurism may be formed by the accidental opening of one of the veins in 

 front of the artery ; or severe neuralgic pain may arise from the operation implicating one of 

 the nervous filaments in the neighborhood. The anterior branch, on the contrary, is sub- 

 cutaneous, is a large vessel, and is readily compressed ; it is consequently more suitable for the 

 operation. 



The Internal Maxillary (Fig. 287), the larger of the two terminal branches of 

 the external carotid, arises from that vessel opposite the neck of the condyle of the 

 lower jaw, and is at first embedded in the substance of the parotid gland ; it passes 

 inward between the ramus of the jaw and the internal lateral ligament, and then 

 upon the outer surface of the External pterygoid muscle to the spheno-maxillary 

 fossa, to supply the deep structures of the face. For convenience of description it 

 is divided into three portions : a maxillary, a pterygoid, and a spheno-maxillary. 



In the first part of its course (maxillary portion] the artery passes horizontally 

 forward and inward, between the ramus of the jaw and the internal lateral ligament. 

 The artery here lies parallel to and a little below the auriculo-temporal nerve; it 

 crosses the inferior dental nerve, and lies along the lower border of the External 

 pterygoid muscle. 



In the second part of its course (pterygoid portion) it runs obliquely forward 

 and upward upon the outer surface of the External pterygoid muscle, being 

 covered by the ramus of the lower jaw and lower part of the Temporal muscle; 

 or it may pass on the inner surface of the External pterygoid muscle to reach the 

 interval between its two heads, between which it passes to reach the spheno- 

 maxillary fossa. 



In the third part of its course (spheno-majrillary portion] it approaches the 

 superior maxillary bone, and enters the spheno-maxillary fossa in the interval 

 between the two heads of the External pterygoid, where it lies in relation with 

 Meckel's ganglion, and gives off its terminal branches. 



The branches of this vessel may be divided into three groups, corresponding 

 with its three divisions. 



BRANCHES OF THE FIRST OR MAXILLARY PORTION (Fig. 288). 



Tympanic (anterior). Small meningeal. 



Deep auricular. Inferior dental. 



Middle meningeal. 



The tympanic branch passes upward behind the articulation of the lower jaw, 

 enters the tympanum through the Glaserian fissure, and ramifies upon the mem- 

 brana tympani, forming a vascular circle around the membrane with the stylo- 

 mastoid artery, and anastomosing with the Vidian and the tympanic branch from 

 the internal carotid. 



The deep auricular branch often arises in common with the preceding. It 

 passes upward in the substance of the parotid gland, behind the temporo-max- 

 illary articulation, pierces the cartilaginous or bony wall of the external audi- 

 tory meatus, and supplies its cuticular lining and the outer surface of the 

 membrana tympani. 



The middle meningeal is the largest of the branches which supply the dura 

 mater. It arises from the internal maxillary, between the internal lateral liga- 

 ment and the neck of the jaw, and passes vertically upward between the two 

 roots of the auriculo-temporal nerve to the foramen spinosum of the sphenoid 

 bone. On entering the cranium it divides into two branches, anterior and poste- 

 rior. The anterior branch, the larger, crosses the great ala of the sphenoid, and 



