314 ZOOTOMY. 



250. The course of the subclavian arteries : each, 

 soon after its origin, divides into the vertebral artery {vr), 

 which dives inwards, and then passes forwards through the 

 vertebrarterial canal of the cervical vertebrae (§ 24), to 

 supply the brain and spinal cord ; and the brachial artery 

 {br), which passes directly outwards, and sends branches 

 to the fore-limb and shoulder-girdle, giving off also the 

 internal mammary artery (a.epg), a small vessel which 

 runs backwards over the inner face of the wall of the 

 thorax just external to the'sternum, 



251. The thoracic arteries, small vessels given off in pairs from 

 the thoracic aorta, and supplying the seven posterior intercostal spaces. 

 The five anterior intercostal spaces are supplied by a branch of the 

 internal mammary. 



252. The phrenic arteries, arising from the aorta and supplying 

 the diaphragm. 



253. The renal arteries (f), of which the right comes 

 off almost immediately posterior to the anterior mesenteric 

 (§ 183), and the left about half an inch posterior to the 

 right; each passes immediately to the hilus (§ 261) of the 

 corresponding kidney, 



254. The renal veins (r), each of which runs parallel 

 and just posterior to the corresponding renal artery, 

 receives a large vein from the dorsal wall of the abdomen, 

 and pours its contents into the postcaval. 



255. The lumbar arteries and veins, small vessels supplying the 

 dorsal walls of the abdomen, and springing from the aorta and post- 

 caval respectively. 



256. The spermatic arteries and veins {spm\ taking 

 their origin somewhat posterioriy to the posterior mesenteric 

 artery, from the aorta and postcaval respectively, and passing 

 to tlie testes (§§ 266 and 268), or ovaries (§ 291). 



257. The median sacral artery [m.sc], a small trunk arising from 



