42 DUST AND ITS DANGERS. 



their usefulness and the various beneficent 

 things which they do, scientific men have seen 

 fit to make them bear the added burden of the 

 name of phagocytes^ 



But to return to our dust particles. In spite 

 of all the safeguards with which our lungs are 

 furnished against the entrance of foreign 

 bodies, into their deep and delicate recesses 

 and through them into the blood, a considerable 

 number of dust particles of one kind or another 

 do get in and permanently lodge upon those 

 walls of the delicate breathing chambers in the 

 lungs, which are beyond the protecting agency 

 of the ciliated cells. Now right in the walls 

 of these tiny air-chambers of the lungs, where 

 the blood is separated from the inbreathed air 

 only by a film, one of the most important and 

 subtle of the vital process goes on, upon which 

 the continued purity and virtue of the blood 

 depends. Here the blood gives up the car- 

 bonic acid and water which it has gathered in 

 its journey around the system, and takes in its 

 fresh supplies of oxygen. 



Although persons who habitually work in 

 very much dust-laden air are liable to pul- 



1 See " The Story of the Bacteria," 



