72 A MANUAL OF ZOOLOGY 



aorta, which, after giving off branches to the kidneys and 

 the reproductive organs, branches into the right and left 

 Common iliacs. Before joining the right aorta the left 

 gives off branches to the stomach, the pancreas, and the 

 mesentery. The pulmonary artery divides near the ventri- 

 cle into a right and a left branch. Trace these branches 

 to the lungs. Notice that they run along by the side of 

 the pulmonary veins, which open into the left auricle. 

 If the specimen is a female a large ovary with eggs in 

 various stages of development will be found immediately 

 dorsal and posterior to the liver. Are there any indica- 

 tions of two ovaries? Can you fihd a way by which the 

 eggs might escape from the body? , About how many eggs 

 are there? On each side of the ovary notice curiously 

 folded bodies. These are the fimbriated- ends of the ovi- 

 ducts. Trace them backward. Where do they open? How 

 do the eggs get into them? How are they fastened to the 

 body wall? Have they any connection with each other? 

 Slit open the oviduct to near its posterior end and note 

 the character of its mucosa. The oesophagus lies back 

 of the trachea and is inclined somewhat to the left of the 

 median line. How does it compare^ in length with that 

 in the frog? Beginning near the mouth, slit open the ali- 

 mentary canal, in situ, until you are convinced by the 

 character of the mucous membrane that you have passed 

 through the oesophagus and the stomach into the small 

 intestine. Compare the mucosa so far with that in the 

 two fishes and the frogs you have examined. Which is 

 the better way to determine the extent of the stomach, the 

 external form or the internal structure? What is the shape 

 of the stomach? How does it compare with the dog-fish? 

 The perch? The frog? In which of these forms is the 

 pyloric valve most highly developed? Where would you 

 look for the pancreas in any vertebrate? Carefully dis- 

 sect it away from the intestine to find the opening of its 

 duct. How are the intestines held in place? Trace back 

 the small intestine, unraveling and slitting it open, until 

 you pass into the large intestine. Could you tell by the 

 chara,cter of the mucosa the limits of the small intestine? 

 Trace back the large intestine by slitting it open until you 

 come to the cloaca. Now open the cloaca along one side. 



