THE STORY OF THE LUNGS, SKIN AND KIDNEYS 87 



possess a microscopic fringe of lash like threads of 

 living matter. These are known as cilia. They are 

 in a state of constant movement and serve to waft 

 up towards the mouth the fluid secretion of the lungs, 

 whilst they also possess a certain effect in clearing 

 the bronchial tubes of minute particles which may be 

 inhaled in the air. These microscopic brushes in 



teryn* 



left bronchiot 



Uit>e 



'powerfully 

 magnified air-ce//* 



Fig. 26. STRUCTURE OF LUNGS SHOWING BRON- 

 CHIAL TUBES ENDING IN AIR CELLS. 



other words possess the function of keeping the 

 bronchial tubes clear. The action of a cough can 

 only be exercised in bringing up from the lungs 

 matter which has been wafted up to the root of the 

 windpipe, and it is due to the action of these cilia 

 that any extra secretion, as in the case of bronchitis, 

 is brought within reach of the cough through the 

 action of which it is expelled from the body. 



