THE INTERNAL MAXILLARY ARTERY 647 
complex course and the large number of branches given off it is convenient to divide 
it into three parts. 
I. The first part is much the longest, forms an S-shaped curve, and is in great 
part in contact with the guttural pouch. It passes upward and forward on the 
medial surface of the mandible a distance of about an inch (ca. 2-3 em.), and is 
related here to the vein, which is ventral. It then turns inward on the ventral 
surface of the lateral pterygoid muscle and the mandibular nerve, passes between 
that muscle and the tensor palati, and runs forward to enter the alar canal. 
This part gives off the following branches: 
1, The inferior alveolar artery (A. alveolaris mandibule s. inferior)! passes 
downward and forward with the homonymous vein and nerve, being at first between 
Fic. 564.—Lerrr Eyre or Horsr, Derper Dissection. 
The outer plate of bone has been removed behind the pterygoid crest to expose the vessels and nerves. a, a, Rem- 
nants of periorbita; b, b, stumps of rectus oculi superior; c, obliquus oculi inferior; d, rectus oculi inferior; e, rectus 
oculi lateralis; e’, retractor oculi; f, rectus oculi medialis; g,g, obliquus oculi superior; h, eyeball; 7, trochlear nerve; 
k, ophthalmic nerve; k’, nasal nerve; #’’, infratrochlear nerve; k’”’, ethmoidal nerve; J, optic nerve; m, frontal nerve; 
n, lacrimal nerve; 0, zygomatic nerve; p, nerve to obliquus inferior (from oculomotor); g, maxillary nerve; 7, infra- 
orbital nerve; s, sphenopalatine nerve; ¢, great palatine nerve; u, small palatine nerve; v, internal maxillary artery; 
w, buccinator artery (cut off); z, infraorbital artery; x’, malar artery; y, spheno-palatine artery; z, great palatine 
artery; 2’, small palatine artery; 1, 2, stumps of zygomatic arch; 3, stump of supraorbital process; 4, facial crest; 
6, temporal fossa; 6, external ophthalmic artery; 7, muscular branch of 6; 8, lacrimal artery (cut); 9, supraorbital 
artery; 10, anterior deep temporal artery; 11, ethmoidal artery. (After Ellenberger-Baum, Top. Anat. d. Pferdes.) 
the lateral and medial pterygoid muscles, then between the latter and the ramus of 
the mandible. It enters the mandibular foramen, passes downward and forward 
in the mandibular canal, and terminates at the mental foramen by dividing into 
mental and incisor branches. The mental branch (A. mentalis) emerges through 
the mental foramen and anastomoses in the lower lip with the opposite artery and 
the inferior labial. The incisor branch (Ramus incisivus) continues forward in the 
bone, supplies twigs to the canine and incisor teeth, and anastomoses with its fellow 
of the opposite side. Collateral branches are detached to the pterygoid and mylo- 
hyoid muscles, and within the bone to the teeth, alveolar periosteum, the gums, 
and the spongy substance of the mandible. 
2. The pterygoid arteries, two or three in number, are distributed to the ptery- 
goid and tensor and levator palati muscles. 
1 Also known as the inferior dental artery. 
