494 SANGUIFEROUS SYSTEM. 



the external carotid of mammalia, over the head and face, 

 the internal carotid artery being here a very small branch to 

 the small contents of the cranial cavity, and, as in other rep- 

 tiles, the vertebral artery is not required to enter the small 

 cranium. The subclavian artery (A. B. d. e.), on each side, 

 also gives off several branches to the neck, and to the scapular 

 and pectoral muscles, the two anterior intercostal arteries, 

 and the internal mammary which, in passing backwards 

 along the interior of the ribs, anastamoses with the inter- 

 costals and with the epigastric artery. A few branches to 

 the dorsal and scapular muscles are given off from the axillary 

 artery in its passage to the inner part of the head of the 

 humerus, where, as brachial artery, it sends off the usual 

 deep and circumflex branches, and on arriving at the elbow- 

 joint, it divides into a small radial and ulnar artery to supply 

 the short fore-arm and hand. 



The right aorta (A. f. B. /.), after leaving the common 

 systemic trunk of that side, passes upwards and backwards 

 to unite with the left aorta (A. g. h. B. g. h.) under the ver- 

 tebral column, and sends off, in this course, one or more 

 intercostal branches. The right and left aortae unite with 

 the right and left branches of the pulmonary artery (B. p. q.) 

 by means of two ductus arleriosi (B. r. s.), which remain, 

 with their canal obliterated, in the adult state. The left 

 aorta (B. g.}, arising by a distinct orifice from the left por- 

 tion of the ventricle, follows a course analogous to the right, 

 without sending off branches to the anterior part of the 

 body, and is appropriated almost entirely to the abdominal 

 viscera, a small communicating branch (B. h.) being alone 

 left to anastomose with the right aorta. From the left arch 

 of the aorta arise three visceral arteries, the gastric or coro- 

 nary artery (B. /.) to the oesophagus and the stomach, the 

 cceliac (B. m.) which sends branches to the liver, the pan- 

 creas, the spleen, and the large intestines, and the mesen- 

 teric artery (B. i.), which is chiefly spread on the mesentery 

 and small intestines. The common trunk of the abdominal 

 aorta (A. B. n. n.}, in passing backwards, gives off a few pos- 

 terior intercostal branches, the two spermatic arteries, se- 

 veral renal branches to the lobulated kidneys, some small 

 lumbar arteries, and a cloacal branch like a posterior me- 

 senteric, and after sending out the large iliac arteries on 



