216 VERTEBRATE ZOOLOGY 



Lying alongside these branches of the portal vein are the much 

 smaller bile ducts, which collect bile from the lobes of the liver. 

 A duct from the gall bladder, called the cystic duct, joins these 

 bile ducts, and the union of all of these forms the common bile 

 duct, which lies alongside the portal vein and carries the bile to 

 the duodenum. Trace these ducts ; if they are not easily seen, they 

 may often be made apparent by squeezing bile into them from 

 the gall bladder. 



The pancreas is a long, flat gland, four or five inches in length. 

 It has two limbs, which lie at right angles to each other. One 

 of these lies in the loop of the duodenum; the other extends to 

 the left side of the body cavity along the dorsal surface of the 

 stomach. The pancreas communicates with the duodenum usu- 

 ally by two ducts. The pancreatic duct, which lies near the bend 

 of the pancreas, joins the common bile duct and enters the duo- 

 denum with it ; the accessory pancreatic duct, which may be want- 

 ing, enters the duodenum about an inch back of the main duct. 



A number of large, soft lymph glands are present in the mes- 

 entery, the largest being about two inches in length and situated 

 near the center of the mesentery ; although it is called the pancreas 

 Aselli, it is not a pancreas. 



Exercise 8. Make a semidiagrammatic sketch showing the dorsal and 

 posterior surfaces of the liver, the pancreas, and the duodenum, 

 the bile and pancreatic ducts, and the branches of the portal vein 

 on the surface of the liver, so far as observed. 



The study of the digestive tract will be finished after that of 

 the portal veins. 



The Vascular System. This system is composed of the follow- 

 ing organs: (i) the heart, (2) the arteries, (3) the veins, (4) the 

 capillaries, and (5) the lymph vessels. The heart is a muscular 

 pump containing two auricles and two ventricles. It drives the 

 blood through two systems of arteries: (a) the pulmonary arte- 

 ries, which take venous blood from the right ventricle to the lungs 

 to be aerated, and (b) the systemic arteries, which take arterial 

 blood from the left ventricle to the various tissues and organs 

 of the body. The heart receives blood through two systems of 



