DUST AND ITS DANGERS. 45 



fully the lungs may stow it away in consider- 

 able quantities, there is a very curious provision 

 against its further entrance to and distribution 

 in the body. This is the way that is provided 

 against. As the blood circulates through the 

 lungs as well as in every other part of the body, 

 a small amount of its fluid part, conveying an 

 abundance of nutriment, oozes out through the 

 walls'of the vessels into all the minute clefts and 

 crannies of the tissues where the cells lie and 

 bathes and nourishes them. Now, having done 

 this, the nutritive fluid which we call lymph 

 is gradually collected into a series of irregular 

 narrow vessels which open into large and still 

 larger trunks until finally it is poured back into 

 the blood, of which it again becomes a part. 



If this lymph which has searched out every 

 remotest corner of the body to which it was 

 distributed should have become contaminated 

 or polluted by any harmful or foreign material 

 which it had come across in the tissues, it would 

 carry it straight back and pour it into the blood, 

 where it might cause dire results, since the 

 blood is an extremely important and delicate 

 juice. But fortunately the lungs, as well as 



