THE DIGESTIVE SYSTEM 17 



of the pharynx and will be located later when it is exposed 

 during the study of the circulatory system. 



The liver is one of the largest of the glands and is an out- 

 growth of the wall of the intestine. It is composed of 

 three lobes. The gall bladder is a greenish or yellowish 

 transparent sac located between its right and middle lobes. 

 The common bile duct should be located in the mesentery 

 just below the gall-bladder and followed forward. It will 

 be found to originate at the gall-bladder. A short cystic 

 duct leads from the gall-bladder and a right and left 

 hepatic duct join it as it passes into the common bile-duct. 

 Posteriorly it passes to the dorsal side of the duodenal 

 wall and runs a short distance caudad imbedded in the wall 

 before it penetrates the cavity of the duodenum. 



The pancreas arises from several outgrowths of the intes- 

 tine proper. The ventral lobe is a white body in the curve 

 of the duodenum and is continuous with the dorsal lobe 

 which is dorsal to the duodenum. The pancreatic duct 

 empties into the intestine on the opposite side from the 

 entrance of the bile-duct. It will be found imbedded in 

 the posterior margin of the ventral lobe of the pancreas. 

 Split open the intestine near this point and try to locate 

 the entrance of the pancreatic and bile ducts. 



C. The Internal Aspects of the Digestive Tract. 



Cut open the stomach and place the contents in a dish. 

 The Little Skate is omnivorous. Hermit and other crabs, 

 shrimps, worms, amphipods, ascidians, bivalve moUusks, 

 squids, small fishes, and other animals may be present in 

 the stomach. 



Cut open the anterior intestine along one side just be- 

 tween the large longitudinal blood vessels found on its wall. 

 The spiral valve is its chief structure. It consists of a fold 

 of the intestinal wall spirally coiled so as to form a series 



