462 



ELEMENTARY ANATOMY, 



[LESS, 



and Porpoises), but with the Saurop'sida also ; while in pos- 

 sessing lungs he agrees with all Vertebrates, except Fishes, 

 which with the exception of the Mud-fish (Lepidosiren] are 

 destitute of true lungs. First, then, may be considered the 

 lungs as they exist in man and Vertebrates generally. After 

 that will naturally follow the consideration of gills, or branchiae, 

 parts which in function answer to the lungs of man, though 

 they have no resemblance in structure or mode of development. 



R. JYK; 



FIG. 391. THE HEART, GREAT VESSELS, AND LUNGS. FRONT VIEW. 



R Bright ventricle; LV, left ventricle: RA, right auricle; LA, left auricle; 

 Ao, aorta r PA, pulmonary artery; PV, pulmonary veins; RL, right lung; 

 LL, left lung ; vSi vena cava superior; SC, subclavian vessels ; C, carotids; 

 R and LJV, right and left jugularveins ; VI, vena cava inferior ; T, trachea ; 

 B, bronchi. All the great vessels but those of the lungs are cut. 



2. The LUNGS of man have been shortly described in 

 the Fourth Lesson of " Elementary Physiology." They are 

 two in number, one placed on each side of the heart, and 

 (with it and the blood-vessels, air-passages, and oesophagus) 

 fill up the entire cavity of the thorax. The lungs are 

 attached, by their roots, to the two branches of the windpipe 

 (hereafter to be described), and to the great vessels proceed- 

 ing to and fro between the lungs and the heart. 



From this attachment each lung hangs down freely sus- 

 pended in a short serous sac the pleura which closely 

 invests it. This is the proper serous sac of the thorax. 



