686 



BLOOD-VASCULAR SYSTEM OF THE HORSE 



The upper one is the transverse facial vein, which unites close to the end of 

 the facial crest. 



A little lower is the large valveless vena reflexa, or alveolar vein. This passes 

 back under the upper part of the masseter on the maxilla, turns around the tuber 

 maxillare, perforates the periorbita, and joins the ophthalmic vein. It is relatively 

 small at each end, but presents one or two large fusiform dilatations. Its posterior 



part is embedded in a mass of fat. It 

 receives the following tributaries : (a) 

 The great palatine vein (V. palatina 

 major), separates from the palatine 

 artery at the anterior palatine fora- 

 men, and passes in the groove between 

 the tuber maxillare and the palate 

 bone. The palatine veins form a very 

 rich plexus of valveless vessels in the 

 submucosa of the hard palate, which 

 consists of several layers anteriorly. 

 (5) The sphenopalatine vein (V. 

 sphenopalatina) is the satellite of the 

 artery; it forms a rich plexus of valve- 

 less vessels on the turbinate bones 

 and the septum nasi. The venous 

 plexuses are remarkably developed in 

 certain parts of the nasal mucosa. 

 On the septum a little below its 

 - middle and on the turbinates the 

 veins are in several layers. The ol- 

 factory region does not share in this 

 arrangement, and the veins here are 

 small and join the ethmoidal vein, 

 (c) The infraorbital vein (V. infra- 

 orbitalis) is also a satellite of the ar- 

 tery; it usually unites with the spheno- 

 palatine to form a short common 

 trunk, (d) The ophthalmic vein (V. 

 ophthalmica) is a short trunk, which 

 is connected in front with the vena 

 reflexa and behind with the cavernous 

 sinus through the foramen orbitale. 

 It receives veins which correspond to 

 the arterial branches. 



The buccinator vein (V. buccin- 

 atoria) extends backward from the ex- 

 ternal maxillary along the ventral bor- 

 der of the depressor labii inferioris and 

 buccinator under cover of the mas- 

 seter, turns medially over the ramus 

 of the mandible about two inches (ca. 

 5 cm.) behind the last molar tooth, and is continued as the internal maxillary vein. 

 It has a large fusiform dilatation and is valveless. It receives a large vein from 

 the buccal plexus, and is usually connected with the masseteric vein. 



The lingual vein (V. hngualis) is formed at the side of the lingual process of the 

 hyoid bone by the confluence of several veins which come from the substance of the 

 tongue. One or two considerable vessels run partly in the substance of the hyo- 



FiG. 5S7. — Dissection of ^Mandibular Space and Ad- 

 jacent Part of Neck of Horse. 

 a, Ramus of mandible; b, sterno-cephalicus muscle; 

 c, c', omo-hyoidei and sterno-hyoidei (portion removed on 

 right side); d, hyoid bone; e, anterior belly of digastricus; 

 /, g, my lo-hy oideus ; h, mandibular lymph glands (portion 

 removed on right side); i, parotid gland; k, mandibular 

 salivary' gland; I, chin; m, occipito-mandibularis; i, parotid 

 duct; 2, facial vein; 5, facial artery; 4, external maxil- 

 lary vein; 5, sublingual vein; (?, sublingual artery; 7, ven- 

 tral branch of first cervical nerve; S, mylo-hyoid nerve. 

 (After Ellenberger, in Leisering's Atlas.) 



