LUNGS. 



9 1 



Organs of respiration. Lungs. As their name indicates 

 (pneumon, from pneo, I breathe), the lungs are the essential 

 organs of respiration. They are two in number, though they 



Fig. 24. Lungs and heart. 



A. Lungs ivith the anterior edges 



turned back to show the heart 

 and bronchia. 



B. Heart. 



C. Aorta. 



D. Pulmonary artery. 



E. Ascending vena cava. 



F. Trachea. 



G, G. Bronchia. 



H, H. Carotid arteries. 



I, I. Jugular veins. 



J, J. Subclavian arteries. 



K, K. Subclavian veins. 



P, P. Costal cartilages. 



Q . An tcrior ca rdiac a rtery. 



R. RigJit auricle. 



receive the air by one canal and the blood by a single vessel ; 

 they maybe considered as the terminal expansion of the rami- 

 fications of the trachea, or as the two heads of a single tree. 

 Placed in the chest, of which they occupy the larger part, 



