VASCULAR SYSTEM 1009 
vertebral column along which it passes, as the aorta descendens, to the 
tail, where it ends as arteria coccygea. 
Each brachio-cephalic artery divides and subdivides thus— 
a. Truncus caroticus, further separating into 
a. Arteria vertebralis, ascending the neck, running through 
the transverse foramina of the cervical vertebrae (SKELETON, 
pp. 852, 853), and anastomosing in the head with the 
cephalic branches of the CAROTIDS (p. 76) ; 
B. Arteria carotis communis, subdivided into the car. externa 
or facialis, and car. interna or cerebralis ; 
b. The Arteria subclavia also separating into 
a. The sterno-clavicular and thoracic arteries ; 
f. The axillary artery, subdivided into the scapular, humeral 
and brachial—the last being composed of the a. wlnaris and 
a. radialis, or principal arteries of the forearm and manus. 
The aorta descendens gives off in succession— 
A variable number of small vessels to the @SOPHAGUS, and inter- 
costal vessels, generally in pairs, to the RIBS and their muscles, 
as well as the strong unpaired cceliac artery for the STOMACH, 
SPLEEN, LIVER and duodenum (pp. 141, 142) beside an a. 
mesenterica superior, also unpaired, supplying most of the small 
intestine. To them follow the right and left principal renal 
arteries, and those for the REPRODUCTIVE ORGANS, while a pair of 
crural arteries each penetrating the first lobe of the KIDNEY and, 
after sending a branch (a. pelvica) in the PELVIS and some of its 
viscera, leaving that bone in front of the ilio-pubic spine, are con- 
tinued as femoral arteries, running along the crural vein on the 
posterior side of the thigh and supplying chiefly the extensor 
muscles. Next to them come a pair of ischiadic arteries, each 
running ventrally past the kidneys and sending branches into their 
middle and lower lobes, as well as to part of the oviduct, after which 
it leaves the pelvis together with the ischiadic nerve through the 
ischiadic foramen and ultimately descends the leg, separating into the 
~ anterior and posterior tibial arteries. Lastly there are a pair of 
arterix pudendx communes, branches of which supply the lateriventral 
muscles of the tail, the CLOACA and copulatory organs, and near the 
place where this pair originate arises also the unpaired a. mesenterica 
inferior, which supplies most of the rectum, part of the C4iCA and part 
of the cloacal region—a peculiar branch, the a. coccygo-mesenterica, 
being directly connected with a branch of the superior mesenteric 
artery. 
ii. Venous. It has been already stated (p. 414) that the venous 
blood is collected and conveyed to the right atrium of the heart by 
3 great trunks. These are composed as follows :— 
Each vena cava superior consists of (1) a vena jugularis which, 
running subcutaneously along the trachea and cesophagus, collects 
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