VASCULAR SYSTEM. 



671 



duodenal loop. Its secretion is gathered by several tubes 

 into the pancreatic duct which opens into the duodenum. 



The mesentery which supports the alimentary canal, is a 

 double layer of peritoneum reflected from the dorsal abdo- 

 minal wall. 



The dark-red spleen (of importance in connection with the 

 blood), lies behind the stomach. In the mesentery, not far 

 from the top of the right kidney, lie a pair of coeliac ganglia, 



which receive nerves from 

 P the thoracic sympathetic sys- 



tem, and give off branches 

 to the gut. 



Vascular System. 



The four-chambered heart 

 lies in the thoracic cavity 

 between the lungs. It is 

 surrounded by a thin peri- 

 cardium, and immediately 

 in front of it there lies the 

 soft thymus, which is larger 

 in the young than in the 

 adult animal. 



By two superior venge 

 cavse, and by the inferior 

 vena cava, the venous blood 

 collected from the body 

 enters the right auricle. 

 Thence the blood passes 

 into the right ventricle 

 through a crescentic open- 

 ing, bordered by a threefold 

 (tricuspid) membranous valve (worked by chordae tendinese 

 attached to papillary muscles projecting from the wall of the 

 ventricle). 



The right ventricle is not so muscular as the left, which 

 it partly surrounds. By its contraction the blood is driven 

 into the pulmonary trunk, whose orifice is guarded by three 

 semilunar valves. During contraction, the tricuspid valves 

 are pressed together, so that no regurgitation into the right 

 auricle can take place. 



Fig. 238. — Duodenum of Rabbit. 

 (From Krause, in part after 

 Claude Bernard.) 



P., Pyloric end of stomach ; g.l'., gal! 

 bladder with bile duct and hepatic ducts ; 

 p.d., pancreatic duct. 



