1 66 VERTEBRATES. 



Draw this view, showing the muscles and blood vessels. 

 (2) Open the muscular walls along the mid-ventral 

 line from the posterior end to the shoulder girdle being 

 careful not to injure the soft breast bone. Cut across near 

 the middle on both sides and turn back the flaps thus expos- 

 ing the vital organs. Do you find the peritoneum? 



II. The Digestive System. — (i) Open the mouth and 

 pass a probe through the esophagus into the stomach. Push 

 the lobes of the liver aside and study the stomach. Note 

 its shape, location, size and color. Compare it with the 

 stomach of the fish. Is it caecalf Carefully trace the in- 

 testine from the stomach down to the anus. In the first 

 fold find a pale V-shaped mass, the pancreas. What is the 

 function of the pancreas? Note the difference between 

 the small and the large intestine and observe the enlarge- 

 ment, the cloaca, above the anal opening. Draw the digestive 

 organs, including the liver and esophagus. 



(2) Study the liver. How many lobes? Do you find 

 the. gall bladder? Where? Describe it. Trace the gall duct 

 from the liver to the intestine. Squeeze out the gall into 

 the intestine. Find the spleen, a dark red body in the mes- 

 entery near the large intestine. Is it connected in any way 

 with the intestine ? 



III. The Organs of Circulation. — (i) The heart is 

 found above the liver. Note its shape and position. Com- 

 pare it with the heart of the fish. The lower pointed part 

 is the ventricular portion, the upper part is the auricular 

 portion. Do these portions appear to be further divided? 

 Study the blood vessels at the auricular end of the heart. 

 The firmer ones are arteries and the flabby ones, the veins. 

 Note the large arterial trunk extending upward and sub- 



