RESPIRATION. 



127 



CHAPTER III. 



Lun TS. Situation. Tissues. Windpipe Glottis. Organ oi 

 Voice. Air-Tubes and Cells. Mucous Membrane. Coughing. 



Interweaving of Air-Vessels and Blood- Vessels. Inspiration 



Expiration. Respiration. Cooperation of Parts. 



278. THE lungs are situated within the chest, which has 

 been now described. There are two lungs, (Pig. XVHI. 

 a, &,) placed one on the right, and the other on the left side 

 of the chest. The heart lies between them, (Fig. XVIII. d,) 

 and these completely fill this cavity. (Fig. V. a, 6, c.) The 

 lungs are very soft and spongy. They contain little or no 

 flesh, but are composed almost exclusively of tubes and cells, 

 which are to be filled, some with blood,, and* others with air. 



FIG. XVIH. Lungs and Heart. 



c ' 



a, Left lung. 

 6, Right lung. 



c, Windpipe. 



d, Heart. 



e, Great artery 

 carrying blood to 

 lungs. 



f, Great vein. 

 ff, Great artery 



carrying blood to 

 the body. 



279. The air-tubes begin at the back part of the mouth 

 and nostrils with a single cylinder, which leads through the 

 neck to the chest; but in the lungs they are divided and sub- 

 divided into smaller arid smaller tubes, which are distrib- 



