THE RESPIRATORY ORGANS 183 



more trouble than one in the head. When serious inflam- 

 mation attacks the lungs, however, we no longer call it a cold. 



Bronchitis. Inflammation in the bronchi or their subdivi- 

 sions in the lungs is called bronchitis. It is really little more 

 than a cold which has reached the smaller air passages of the 

 respiratory organs, but it produces much trouble there; for 

 many of the tubes are small and any inflammation or secretion 

 fills them more easily and quickly than the same amount would 

 the larger passages of the nose. In the case of a little child 

 or an old person bronchitis may cause severe illness, or even 

 death; but with those of middle age it is not much more 

 serious than a severe cold, although it produces more dis- 

 comfort and more distressing symptoms and is more lasting. 



Pneumonia. If the inflammation extends still farther into 

 the lungs, it is liable to develop into a far more serious disease, 

 called pneumonia. While this is a germ disease, and cannot 

 therefore be originated by a cold, a cold often prepares the 

 lungs for the ready implantation of the pneu- 

 monia bacteria. These bacteria are common in 



the mouth and throat (Fig. 100 a), but if the 

 lungs are healthy, the germs may be inhaled 

 without harm. When, however, the tiny air sacs J 

 in the lungs are inflamed by a cold, their sur- 

 faces offer a place where these pneumonia germs F 10Q _ 

 can get a foothold. Developing there, they may T ^ E ' BAC> | 

 soon produce violent inflammation accompanied TERIA OP 

 by high fever. Secretions accumulate in the air PNEUMONIA 

 sacs, filling them partially or wholly, so that ^ THEBAC- 

 portions of the lungs may become practically TERIA OI 

 solid and breathing sometimes be difficult. Of ^osis 

 course, if all the air sacs were thus filled, death 

 would at once result; but it generally happens that only cer- 

 tain places in the lungs are affected. After a time, if the 

 trouble is not too severe, the liquid mass in the lungs begins 

 K) be absorbed, and eventually the lungs may clear up en* 



