THE INTERNAL ILIAC AHTERIES. 623 



two pillars of that nruacle. In the abdomiiinl cavity, close to the anterior niesenterif, the aorta 

 gives off a branch tliat soon divides into two: one is diaphragmatic, and descends on the 

 posterior face ot that ranscle; the other reaches the sublunibar rej^ioii, passes over the psoas 

 muscle, and traverses the abdominal wall in tlic vicinity of the transverse processes of the 

 luml)ar veitebrsB. VVe will speak presently of tlie middle sacraL 



B. VisCKRAL Branches. — I have not found in the Dog any special bronchial arteries; but 

 there are four vr five oenophageal arteries tliat arise from different points of the tl. oracle aorta ; 

 they descend into the mediastinum, to the right and left of the oesophagus, to which they are 

 distributed. They furnisli branches that accompany the bronchi and enter the lungs. 



The cceliac axis is again divided into three branches, as follows : The gastric, or stomachic 

 coronary artery, dues not divide into two brandies (anterior and posterior gastric) as in Solipids. 

 Ni ar its origin it furnishes a pancreatic branch ; then it expends itself in a great number of 

 filaments that are spread over the posterior face and great tuberosity of the stomach, or over 

 its anterior face after crossing the small curvature. 



The splenic artery readies tlie spleen at the middle of its upper border. It gives on its 

 course: 1. A splenic branch that enters the upper extremity of that organ. 2. The left gastro- 

 omental. The hepatic artery provides the principal hepatic vessel at the posterior fissure of 

 the liver; it is then continued by the right gastro-omerital artery. On the duotlenum, the 

 latter gives origin to the pyloric and the pancreatico-duodenal branches ; the latter is volu- 

 minous, is lodged in the substance of the pancreas, and anastomoses by its last filaments with 

 the anterior mesenteric. 



Tile a;(<t'r(or mesenteric artery arises in the vicinity of the coeliac axis; it forms a curve 

 with the convexity backward, and anastomoses by its extremity with the pancreatico-duodenal 

 brancli of tlm hepatic. From its convexity are detached several filaments (filaments to the 

 small intestine), that form arches towards the smaller curvature of tiiat viscus. Beliind, and 

 at a short distance from its origin, it gives a branch to the caecum and branches to the colon ; 

 the latter are sometimes large. 



The posterior mesenteric commences near the termination of the aorta, and divides into two 

 branches — one passing forward, the other backward ; they form the hsemorriioidai vessels 

 (see Fig. 290). 



Theie is nothing special to note with regard to the renal an. I .spermatic arteries. 



Comparison of the Aorta of Man with that of Animals. 



The aorta in Man offers the same general arrangement 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 limbs— which will 

 be noticed hereafter; and the parietal and visceral branches to the chest and abdomen. At 

 first these are tlie 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 witii the left bronchus ; 

 the right originates alone or in common with the preceding, and enters on the right bronchus. 

 2. The o'.snphageal arteries, disposed somewhat as in the Dog. 3. The cceliac trunk, the 

 distribution of which is nearly identical with tliat of the Carnivora. 4. The superior or great 

 mesenteric, disposed in arches as in the Dog (see Fig. 2St2, 9). Its last branches pass to the csecuiu, 

 and the ascending aud origin of the transverse portion of the colon. 5. Tlie inferior or small 

 mesenteric, which arises troin 1^ to 2 inches :rom the bifurcation of the aorta ; this artery tle»cends 

 into the me o-C(don, and terminates on the sides of the reetum by the haemorrhoidal vessels; 

 to the left, they emit branches to the large intestine; the first iisct-nd along the descending 

 colon, and anastomose on the transverse c^don with the right colic branch of the superior 

 mesenteric. 6. The renal and capsular arteries, which do not offer important differences. 7. 

 1 astly, the spermatic arteries, which ar remarkable for the length of their course, commencing, 

 as tiiey do, at tlie aorta, a short distauu-e below the renal vessels. 



Article III. — Internal Iliac Arteries, or Pelvic Trl'nks 

 (Figs. 338, 368, 370). 



The two internal iliac arteries represent the middle or internal branches of 

 the quadrifnrcation formed by the posterior aorta at its terminal extremity. 



