RESPIRATION 



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the dissolved oxygen in the water. Insects took their air directly 

 into the tissues and blood by way of their numerous complicated 

 air tubes and so got along with a simple circulation. In the birds 

 and mammals this is reversed and the air comes to one place only 



FIG. 122. Bronchi and lungs, posterior view, showing position of heart. 

 1, 1, summit of lungs; 2, 2, base of lungs; 3, trachea; 4, right bronchus; 5, 

 branch to upper lobe of lung; 6, branch to lower lobe; 7, left bronchus; 8, 

 branch to upper lobe; 9, branch to lower lobe; 10, left branch of pulmonary 

 artery; 11, right branch; 12, left auricle of heart; 13, left superior pulmonary 

 vein; 14, left inferior pulmonary vein; 15, right superior pulmonary vein; 

 16, right inferior pulmonary vein; 17, inferior vena cava; 18, left auricle of 

 heart; 19, right ventricle. (After Sappey.) From Kellogg. 



(the lungs), while a complex circulation carries the oxygen to all 

 parts of the body. 



Organs of Breathing. The organs concerned with breathing 

 motions can be placed in two groups, (1) those concerned with 

 holding and carrying the air, and (2) those which change the size 

 of the chest cavity, causing the air to circulate. 



