538 THE ARTEEIE8. 



COMPAEISON OF THE AORTA OF MAN WITH THAT OF ANIMALS. 



The aorta in Man offers the same general disposition as in the Carnivora, the trunk 

 being inflected across, to be placed along the body of the dorsal and first lumbar vertebrae, 

 where it terminates in the iliac vessels. 



It furnishes the coronary arteries, the arteries of the head and thoracic members 

 which will be noticed hereafter ; and the parietal and visceral branches to the chest and 

 abdomen. At first these are the intercostals, beyond the third space ; the diaphragmatic 

 arteries, superior and inferior according as they occupy one or other face of the diaphragm ; 

 and, lastly, the lumbar arteries. 



Among the visceral branches are distinguished: 1, The bronchial arteries, two in 

 number; the left arises from the concavity of the aortic arch, and enters the lungs with 

 the left bronchus ; the right originates alone or in common with the preceding, and enters 

 on the right bronchus; 2, The ce.sophageal arteries disposed somewhat as in the Dog; 

 .3, The cceliac trunk, whose distribution is nearly identical with that of the Carnivora ; 

 4, The superior or great mesenteric, disposed in arches as in the Dog (see Fig. 276, 9). Its 

 last branches pass to the csecum, and the ascending and origin of the transverse portion of 

 the colon ; 5, The inferior or small mesenteric, which arises 1^ to 2 inches from the bifur- 

 cation of the aorta ; this artery descends into the meso-colon, and terminates on the sides 

 of the rectum by the hsemorrhoidal vessels ; to the left, they emit branches to the large 

 intestine ; the first ascend along the descending colon, and anastomose on the transverse 

 colon with the right colic branch of the superior mesentetdc ; 6, The renal and capsular 

 arteries, which do not offer important differences ; 7, Lastly, the spermatic arteries, which 

 are remarkable for the length of their course, commencing, as they do, at the aorta, a 

 short distance below the renal vessels 



ARTICLE III. INTERNAL ILIAC ARTERIES OR PELVIC TRUNKS. (Fig. 277, 2.) 



The two internal iliac arteries represent the middle or internal branches 

 of the quadrifurcation formed by the posterior aorta at its terminal extremity. 



Extending from the body of the last lumbar vertebrae, to near the 

 terminal insertion of the small psoas muscle, in an oblique direction 

 downwards, outwards, and backwards, these arteries correspond : in front, 

 with the trunks of the common iliac veins, which separate them from the 

 external iliacs ; inwards, to the peritoneum ; above and outwards, to the 

 sacro-iliac articulation and to the ilium. 



In its course, the internal iliac artery emits the following branches : the 

 umbilical artery, artery of the bulb, ileo-lumbar, gluteal, and subsacral arteries. 

 At its terminal extremity, it is divided into two branches which ride on the 

 superior border of the tendon belonging to the small psoas muscle : the one 

 within, the other without that tendon. The first is the obturator artery, the 

 second the ileo-femoral artery. All these branches will be studied in the 

 order of their enumeration. 



Preparation of the internal iliac artery. Place the subject in the first position; 

 remove one of the posterior limbs, leaving the rectum and bladder in the pelvis, and 

 slightly inflating the latter organ. Dissect, on the side from which the limb has been 

 removed, the origin and visceral ramifications of the branches furnished by the trunk of 

 the artery. Follow, on the opposite side, the ramifications given off by these branches to 

 the muscles. To conveniently prepare the coccygeal arteries, it *is necessary, after 

 removing the great sciatic ligament and dissecting the internal artery of the bulb along 

 with the subsacral trunk, to raise up the rectum and bladder by means of the chain-hooks. 



. Umbilical Artery. (Figs. 274, 5 ; 277, 3.) 



This artery forms a considerable vessel during foetal life, and carries the 

 blood of the foetus to the placenta ; it will be described in detail in the 

 anatomy of the foetus. 



In the adult it is almost entirely obliterated, appearing only as a fibrous 

 cord extending from the internal iliac artery to the fundus of the bladder, 

 and placed at the free margin of the lateral serous fold detached from the 



