THE PIGEON 185 



Behind the reproductive organs, lying in the cavity of the 

 roof of the body, are found the soft kidneys. What is their 

 position? How many? How many divisions in each? Do 

 you find a duct leading from the kidneys? Where does it 

 go? 



Draw kidneys (Xi)- 



II. The Heart. — Cut open the pericardium if it has not 

 been already destroyed. Note the rough outside and the 

 soft inside enclosing a thin oily substance. This lubricates 

 the heart while it is engaged in its ceaseless work of pump- 

 ing the blood through the body. Can you tell which is the 

 right and which is the left side of the heart? Lay the 

 heart down with the point toward you and the blood vessels 

 from you. Trace the line of fat around the upper part of 

 the heart. Above this are the auricles, small chambers with 

 flabby walls. Can you find blood vessels opening directly 

 into them? How many empty into each? Which side of 

 the heart is the hardest? Compress it with the fingers to 

 find out. The soft side is the right side and the hard, the 

 left. Lay the heart before you in its natural position and 

 draw (X2). Cut the end off about a half inch from 

 the point. Note the relative development of the right and 

 left ventricles. Why is this ? Look at the upper part of the 

 heart. From which ventricle does the great aorta come? 

 From which does the pulmonary artery come? 



The blood leaving the aorta is carried by the arteries to 

 the capillaries in all parts of the body and comes back 

 through the venae cavae. What ventricle sends it? What 

 auricle receives it ? The blood leaving the pulmonary artery 

 is carried through the capillaries in the lungs and comes 

 back through the pulmonary veins. What ventricle sends 



