THE PIGEON 177 



The Arteries. Study the dorsal aorta and its branches. Remove 

 the postcaval vein, taking care not to injure the arteries. The 

 dorsal aorta forms an arch over the right side of the heart and the 

 right bronchus, and reaches a dorsal position between the two 

 lungs, whence it runs backward to the hinder part of the abdominal 

 cavity. Dissect it free and find its branches ; cut the right bron- 

 chus near the lung ; remove the thick peritoneal membrane which 

 covers it. 



The dorsal aorta gives off the following branches : several pairs 

 of small costal arteries, and the coeliac, anterior mesenteric, ante- 

 rior renal, femoral, sciatic, posterior mesenteric, internal iliac, and 

 caudal arteries. 



The coeliac artery is a median vessel which leaves the dorsal 

 aorta near the hinder end of the heart and runs back in the mes- 

 entery, sending off branches to the stomach, liver, pancreas, giz- 

 zard, and anterior part of the intestine. The anterior mesenteric 

 is a large median artery which leaves the dorsal aorta a short dis- 

 tance back of the coeliac artery and runs back in the mesentery, 

 sending branches to the greater part of the intestine. The anterior 

 renal arteries are a pair of small vessels which leave the dorsal 

 aorta opposite the anterior lobes of the kidneys, which they enter. 

 The femoral arteries are a pair of vessels which leave the dorsal 

 aorta behind the anterior renals and pass above the kidneys to 

 the muscles of the thigh. 



The sciatic arteries are a pair of large vessels which leave the 

 dorsal aorta opposite the middle of the kidneys and pass between 

 their middle and posterior lobes to the legs; each gives off a 

 branch to the middle lobe and one to the posterior lobe of the kid- 

 ney. Follow one of these arteries into the leg. The median posterior 

 mesenteric artery and the paired internal iliac arteries leave the 

 aorta together near the hinder end of the kidneys, the former 

 going to the rectum and cloaca, the latter to the muscles of the 

 pelvis. The posterior end of the dorsal aorta is the caudal artery, 

 which supplies the tail. 



Exercise 14. Draw a semidiagrammatic sketch of the dorsal aorta 

 and its branches, so far as these have been observed, together with 

 an outline of the organs in which they lie. 



