642 BLOOD-VASCULAR SYSTEM OF THE HORSE 
branches also to the medial pterygoid and occipito-mandibularis muscles and the 
parotid gland. 
2. The external maxillary artery (A. maxillaris externa)! arises from the ex- 
ternal carotid on the deep surface of the posterior belly of the digastricus (Fig. 561). 
It runs downward and forward on the lateral wall of the pharynx across the deep face 
of the stylo-hyoideus toward the great cornu of the hyoid bone, accompanied by 
the glosso-pharyngeal nerve in front and the hypoglossal nerve behind. After 
giving off the lingual artery at the posterior border of the great cornu, it inclines 
more ventrally on the medial surface of the medial pterygoid muscle, crosses over 
the hyo-glossus muscle, the hypoglossal nerve, the mandibular duct, and the inter- 
mediate tendon of the digastricus, and turns forward in the mandibular space. 
Here it lies on the lower part of the medial pterygoid muscle, and is related medially 
to the mandibular lymph glands, above to the anterior belly of the digastricus, and 
below to the homonymous vein. At the anterior border of the masseter it turns 
around the ventral border of the jaw and ascends on the face in front of that 
muscle. At the turn the artery is in front, the vein in the middle, and the parotid 
duct posterior. The artery is conveniently placed at its inflection. for taking the 
pulse, since it is superficial and lies directly on the bone. Beyond this point it is 
commonly termed the facial artery (A. facialis). The artery and vein pass upward 
along the anterior border of the masseter, under cover of the facial cutaneus and 
the zygomaticus, and are crossed superficially by branches of the facial nerve and 
deeply by the parotid duct. The artery terminates over the levator labii super- 
loris proprius by dividing into the dorsal nasal and the angular artery of the eye. 
The chief branches of the external maxillary are as follows: 
(1) The pharyngeal artery (A. palatina ascendens) arises usually behind the 
stylo-pharyngeus, passes between that muscle and the great cornu, and runs for- 
ward on the lateral wall of the pharynx under the elastic pharyngeal fascia. It is 
distributed to the pharynx, soft palate, and tonsil. 
(2) The lingual artery (A. lingualis) is a large branch which diverges from the 
parent trunk at an acute angle, runs along the ventral border of the great cornu 
of the hyoid bone, and dips under the hyo-glossus muscle. It then passes across 
the kerato-hyoideus, turns inward under the intercornual joint of the hyoid bone, 
and runs forward in the tongue between the hyo-glossus and genio-glossus. This 
part (A. profunda linguz) is flexuous and is accompanied by branches of the hypo- 
glossal and lingual nerves. It is the chief artery of the tongue, and anastomoses 
with the opposite artery and the sublingual.* 
(8) The sublingual artery (A. sublingualis) is a smaller vessel which arises at 
the anterior extremity of the mandibular gland (Fig. 561). It passes forward on the 
anterior belly of the digastricus, between the ramus of the mandible and the mylo- 
hyoideus, perforates the latter, runs along the lower border of the sublingual gland, 
and ramifies in the mucous membrane of the anterior part of the floor of the mouth. 
It detaches branches to the muscles and skin in the mandibular space, the mandib- 
ular lymph glands, and the sublingual gland. It also gives off the small submental 
artery (A. submentalis), which runs forward superficially toward the lower lip, 
supplying twigs to the skin and the mylo-hyoideus. 
In some cases the sublingual artery arises from the lingual and the submental from the | 
external maxillary. Sometimes the sublingual remains on the superficial face of the mylo-hyoideus _ 
—thus resembling the submental of man—and the sublingual gland is supplied by a special 
branch of the lingual. 
1 Also termed the submaxillary or facial artery. The term facial may be applied to the artery | 
after it reaches the lateral surface of the face. | 
2 In exceptional cases the vein is in front of the artery. | 
3 In some cases the lingual trunk runs on the superficial face of the hyoglossus instead of | 
passing beneath it; in such specimens a small branch extends forward a variable distance under | 
the muscle. 
