VEINS OF THE HEAD AND NECK—JUGULAR VEINS 683 
1. The last fourteen dorsal intercostal veins (Vy. intercostales dorsales) of the 
right side go directly to the vena azygos; but on the left side a variable number 
(four to seven usually) at the end of the series go to the vena hemiazygos when that 
vessel is present. 
2. The vena hemiazygos arises from a branch of the left first lumbar vein and 
twigs from the crura of the diaphragm. It passes forward through the hiatus 
aorticus and continues along the left dorsal face of the aorta, and about the mid- 
dle of the back joins the vena azygos. It receives the last four to seven dorsal 
intercostal veins of the left side. It is inconstant and variable. In its absence 
its tributaries join the vena azygos. 
3. The cesophageal vein (V. cesophagea), satellite of the cesophageal artery, 
joins the vena azygos as it inclines downward. 
4. The bronchial vein (V. bronchialis) unites with the preceding to form a 
short common trunk, or, according to Chauveau, empties into the great coronary 
vein. The author is unable to find in the horse any distinct bronchial vein 
emerging at the root of the lung.’ 
VEINS OF THE HEAD AND NECK 
JUGULAR VEINS 
The jugular veins (Vv. jugulares), right and left (Fig. 556), arise behind the 
ramus of the mandible, about two and a half inches (ca. 6-7 cm.) below the tem- 
poro-mandibular articulation by the union of the superficial temporal and internal 
maxillary veins. Each passes downward and backward, at first embedded more 
or less in the parotid gland, and continues in the jugular furrow to the thoracic 
inlet, where it unites with its fellow and the two brachial veins to form the anterior 
vena cava. In the neck it is covered by the skin, fascia, and cutaneus muscle, and is 
superficial to the carotid artery, from which it is separated in the anterior half of 
the region by the omo-hyoideus muscle.” It contains valves at the mouths of its 
tributaries, and has several pairs of semilunar valves variably disposed along its 
course. Its tributaries are as follows: 
1. The internal maxillary vein (V. maxillaris interna) is larger than the external 
maxillary. It may be considered to begin as the continuation backward of the 
buceinator vein where that vessel crosses the alveolar border of the mandible, 
about two inches (ca. 5 em.) behind the last molar tooth. It runs backward on 
the medial surface of the ramus ventral to the lateral pterygoid muscle, and covered 
by the medial pterygoid muscle for a distance of about three inches (ca. 7-8 cm.), 
then inclines a little downward and runs ventral to the artery for about an inch 
(ca. 2-3 em.). It crosses the lateral face of the artery at the posterior border of 
the jaw, and is joined by the superficial temporal vein to form the jugular. Its 
principal radicles are the following: 
(1) The dorsal lingual vein (V. dorsalis linguz) is not a satellite on any artery, 
1 In Chauveau-Arloing-Lesbre the statement is made that ‘‘the bronchial veins, which ramify 
on the bronchi like the arteries of which they are satellites, open into the great coronary vein very 
near its mouth, after having united to form a single vessel, which sometimes opens directly into 
the atrium.” The arrangement is not illustrated. Ellenberger and Baum state that the bronchial 
and cesophageal veins open into the vena azygos separately or by a common trunk. Martin de 
scribes a short broncho-cesophageal trunk, but the vein which he figures as the bronchial does not 
come from the lungs, but is a small mediastinal vessel. The author finds such a vessel usually 
entering the terminal part of the cesophageal vein, but no distinct bronchial vein in the horse. 
Eos statement and figure in Bossi’s recent work agree substantially with those of the German 
authors. 
; * There is usually only one jugular vein on each side in the horse, but in some cases there is an 
internal or deep jugular vein which accompanies the carotid artery and ends at the confluence of 
the external jugulars. M’Fadyean records a case in which the vein lay on the deep face of the 
omo-hyoideus with the carotid artery. This would appear to be an instance of remarkable de- 
velopment of the internal jugular in place of the usual external jugular vein. 
