288 HUMAN PHYSIOLOGY CHAP. 



If the inhaled tubercle bacilli find favorable 'condi- 

 tions for their development, they multiply rapidly, causing 

 inflammation and later the formation of tubercles in 

 different parts of the lungs. Unless the disease is 

 checked the tissues of the lungs become so involved 

 that they cannot carry on their functions properly. The 

 bacteria produce poisons which tend to undermine the 

 health, and cause a loss of appetite and general debility. 

 The disease usually begins with what is called a " cold 

 on the lungs " and a cough. From the very first all 

 excretions from the mouth and nose contain the germs 

 and are the chief source of danger. 



196. Pneumonia. A specific germ is the cause of 

 pneumonia. Pneumonia occurs both in hot and cold 

 climates. In the northern part of 

 our country it occurs chiefly in late 

 winter and early spring. The germs 

 are inhaled with the air and lodge in 

 the air passages of the lungs, where 

 they multiply very rapidly if condi- 

 tions are favorable. Exposure to cold 

 FIG. 156. -Bacteria of and mo i st ure, and general debility 



pneumonia. 



due to exhaustion, alcoholism, or dis- 

 eases of certain kinds, precede an attack of pneumonia. 

 All such conditions tend to cause congestion and inflam- 

 mation in the lungs, and in this way a good soil is 

 prepared for the germs of this dangerous disease. We 

 know that the excessive use of alcoholic beverages may 

 predispose the body to this disease. 



A person is not likely to contract pneumonia if he eats 



