THE RABBIT 289 



a pair of large vessels which go to the kidneys, each renal sending 

 off near its base a large branch, the adrenolumbar artery, to the 

 suprarenal gland and the muscles of the body wall ; the superior 

 mesenteric artery, a large median vessel which arises from the 

 aorta just in front of the renals and subdivides into a large number 

 of branches, which lie in the mesenteries alongside the branches 

 of the portal vein and supply the pancreas and most of the in- 

 testines with arterial blood ; and the coeliac artery, a large median 

 vessel which arises from the aorta a short distance in front of the 

 superior mesentery and just posterior to the diaphragm. The 

 coeliac first sends the small phrenic arteries to the diaphragm and 

 then gives off the large splenic artery— which runs to the spleen but 

 also sends branches to the stomach and the pancreas— and the left 

 gastric artery (or arteries), which go to the stomach and the 

 oesophagus; finally the coeliac becomes the hepatic artery and, 

 after first giving rise to the large gastroduodenal artery (which 

 sends branches to the duodenum, the stomach, and the pancreas) 

 and the small right gastric artery (which goes to the stomach), 

 passes into the liver, where its branches accompany those of the 

 bile duct and the portal vein. 



Exercise 13. Draw a diagram of the abdominal aorta and its branches, 

 so far as observed. 



The Thoracic Cavity. Cut away the ventral and lateral walls 

 of the thorax and thoroughly expose its cavity, but do not remove 

 the diaphragm. The heart will be seen in its pericardium. Im- 

 mediately in front of them is an elongated pinkish organ, the 

 thymus gland. It varies much in size in different animals : in young 

 animals it may project over the heart, whereas in old animals it is 

 much smaller and may be almost entirely wanting. On each side 

 of the heart will be seen the pleural sac with the lung. 



Examine the diaphragm carefully. Note its position in the body 

 cavity; its form is cup-shaped, the opening of the cup looking 

 toward the abdominal cavity. It will be seen to consist of a thin 

 plate of muscle surrounding a transparent central tendon. Note 

 the openings in the diaphragm through which the postcaval vein, 

 the aorta, and the oesophagus pass. 



