40 DUST AND ITS DANGERS. 



in rapidity and force when the body is active. 

 Almost every one has noticed that shortly after 

 rising more or less mucus or " phlegm " is apt 

 to come up into the throat. This is because the 

 increasing vigor of the ciliary movement, as 

 one's general activity increases, sweeps up the 

 accumulation which the comparative quiescence 

 of the night has allowed to form. 



It is a curious thing that these humble but 

 energetic little members of the cell communi- 

 j ties which make up the body are apparently the 

 I last elements to die when what we sometimes 

 call the vital forces no longer act. The breath 

 ceases, the heart flutters and is still, the blood 

 ebbs and flows a little here and there, the last 

 definite nerve impulses express themselves as 

 now one now another muscle quivers or feebly 

 and fitfully contracts, but still these wonderful 

 little cilia keep swinging on sometimes for 

 hours after all trace of what we have called 

 life has disappeared, and when these too at 

 last are still, and not till then, is life in the 

 body totally extinct. 



There is another very curious arrangement 

 in the air passages for the disposition of small 



