34 HUMAN BIOLOGY 



digested and nutritious food, like eggs and milk, sleep and 

 freedom from hard muscular work and from worry. These 

 conditions may be obtained even in crowded cities, for by 

 the use of tents on the roof, or of window tents (Fig. 15) a suffi- 

 cient amount of air may be secured, and almost marvelous 

 cures are found to result. 1 



29. The cause and treatment of pneumonia. Another 

 disease that affects the lungs is pneumonia. It is more 

 prevalent in the spring and autumn of the year, and is 

 commonly a disease of adults. The cause of pneumonia is a 

 spherical form of bacteria, which get into the lung tissue 

 and grow there when the individual is physically weak or 

 mentally depressed. Formerly, in treating the disease, 

 patients were kept in closed rooms, carefully shielded from 

 all draughts of air. It has been found, however, as is the 

 case with tuberculosis, that fresh outdoor air is one of the 

 best means of treating the patient. To combat both tuber- 

 culosis and pneumonia, our bodies and minds should be kept 

 in such a healthy and vigorous condition that invading dis- 

 ease germs will always meet with a hostile reception whenever 

 they attempt to prey upon our organs and tissues. 



30. Cause of diphtheria. Another disease that formerly 

 claimed many victims among young children is diphtheria. 

 The germs of this disease are rod-shaped organisms some- 

 what larger than those that cause tuberculosis. When these 

 bacteria find lodgment and grow in the throat, they produce 

 a membrane and form poisonous substances known as toxins, 

 which are absorbed and carried by the blood to other parts of 

 the body, often causing paralysis and other injurious effects. 



1 The authors are much indebted to Dr. Thomas Spees Carrington 

 for suggestions relating to tuberculosis. For additional suggestions 

 see Dr. Carrington's " Fresh Air and How to Use It " ($ 1), National 

 Association for the Study and Prevention of Tuberculosis, 105 E, 

 22d St., New York City. 



