552 



BLOOD-VASCULAR SYSTEM OF THE HORSE 



of the mandible about two inches (ca. 5 cm.) below the articulation of the jaw 

 and ends in the anterior part of the pterygo-palatine fossa. On account of its 

 complex course and the large number of loranches given off it is convenient to divide 

 it into three parts. 



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 

 inner surface of the mandible a distance of about an inch (ca. 2 to 3 cm.) and is 

 related here to the vein, which is ventral. It then turns inward below the external 

 pterygoid muscle and the inferior maxillary nerve, passes between that muscle 



and the tensor palati, and runs forward 

 to enter the alar (pterygoid) foramen. 

 This part gives off the following l)ranches: 



1. The inferior alveolar or dental 

 artery (A. alveolaris mandibulse s. in- 

 ferior) passes downward and forward 

 with the homonymous vein and nerve, 

 being at first between the external and 

 internal 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 fora- 

 men by dividing into mental and incisor 

 branches. The mental branch (A. men- 

 talis) emerges through the mental fora- 

 men and anastomoses in the lower lip 

 with the opposite artery and the inferior 

 labial. The incisor branch continues for- 

 ward in the bone, supplies twigs to the 

 canine and incisor teeth, and anastomoses 

 with its fellow of the opposite side. Col- 

 lateral branches are detached to the ptery- 

 goid 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 

 pterygoid and tensor and levator palati 

 muscles. 



3. The tympanic artery is a very 

 small vessel which passes along the 

 Eustachian tube to the petro-tympanic 

 fissure (of Glaser) and enters the middle 

 ear. 



4. The middle meningeal artery (A. meningea media) arises beneath the buc- 

 cinator nerve where the internal maxillary turns forward. It passes backward 

 across the temporal wing of the sphenoid to the antero-external part (foramen 

 spinosum) of the foramen lacerum. Entering the cranium, it divides into branches 

 which course in the grooves on the temporal and parietal bones and supply the 

 dura mater. It anastomoses with the posterior meningeal. 



The size of this artery is variable, and is in inverse ratio to that of the posterior meningeal. 



5. The posterior deep temporal artery (A. temporalis profunda aboralis) 



Fig. 438. — Right Eye op Horse. 

 a. Remnants of periorbita; b, levator palpe- 

 bral superioris; c, obliquus oeuli inferior; d, rectus 

 oculi inferior; e, rectus oeuli externus; /, rectus 

 oouli .superior; g, sclera; g,' cornea; h, lacrimal 

 gland; i, frontal nerve; k, frontal artery; I, branch 

 of lacrimal nerve to gland; m, lacrimal artery; ?i, 

 zygomatic nerve; o, branch of ophthalmic artery; 

 p, branch of oculomotor nerve to obliquus oculi 

 inferior; q, maxillary nerve; /', infraorbital nerve; 

 s, posterior nasal nerve; t, great palatine nerve; 

 II, small palatine nerve; i\ internal maxillary artery; 

 w, buccinator artery (cut); x, infraorbital artery; 

 J-', malar artery; y, sphenopalatine artery; 2, great 

 palatine artery; 2', small palatine (or staphyline) 

 artery; 1, posterior deep temporal artery; 2, 3, 

 stumps of orbital margin; 4, facial crest; 6, temporal 

 fossa; 6, foramen lacerum orbitale; 7, anterior end of 

 alar canal; 8, posterior opening of same. (After 

 EUenberger, in Leisering's Atlas.) 



