266 



THICK WIND. — BSOKEN WIND. 



The annexed diagram will clearly illustrate the phenomena 

 in question : — Let the reader suppose the tube a to be the 

 windpipe, and the small tubes 66 the right and left bronchial 

 tubes passing into cc, the right and left lungs : dd to be the 

 outer or investing membrane 

 of the lungs, and being in close 

 contact with the same at every 

 part of their surface ; while 

 eeeeee are dotted lines to show 

 the direction of the lungs ccj 

 seen beneatli this outer or in- 

 vesting membrane. 



Now the'lungs, as most in- 

 telligent people are aware, are 

 light, spongy bodies, containing 

 innumerable passages through 

 which the air freely circulates, 

 and by means of which the 

 purification of the blood within 

 the pulmonary organs is con- 

 stantly affected. The lungs are 

 also highly elastic bodies, and 

 their outer or investing mem- 

 brane (membrane dS), is like- 

 wise so constituted as to be 

 readily adapted to the varying 

 size of the lungs, arising from 

 the inspiration and the expira- 

 tion of the air. To the reflective 

 reader it will be evident that 

 air passing down the tube a,and 

 entering the lungs through the 



Vig. 19. 

 A diagram showing the position 

 of the lungs and their outer or invest- 

 ing membrane, 



a The Trachea. 

 65 The right and left bronchial 



tubes goiug to. 

 (X The right and left lungs. 

 M The outer or investing mem- 

 brane of the lungs, 

 ceccce Dotted Hues showing the direc- 

 tion of the lungs cc heneaih, 

 their investing membrane. 



