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 carotims, 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) ; 

 (S. Arteria carotis communis, subdivided into the car. externa 

 or facialis, and car. interna or cerebralis ; 

 h. The Arteria subclavia also separating into 

 a. The sterno-clavicular and thoracic arteries ; 

 /3. The axillary artery, subdivided into the scapular, humeral 

 and brachial — the last being composed of the a. ulnaris 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 CESOPHAGUS, 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, sujiplying 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 

 arterise pudendse commmies, 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 

 inferim', which supplies most of the rectum, part of the CiECA and part 

 of the cloacal region — a jjeculiar 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 cesopliagus, collects 



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