466 MAN CONTROLS HIS ENVIRONMENT FOR HEALTH 



with little ventilation. Children of tubercular parents are often 

 handicapped by a weak constitution and are therefore very sus- 

 ceptible to the disease. 



Practical Exercise 6. Tuberculosis is said to be a social disease. Explain 

 this statement. 



Project. To determine the seasonal variation in the number of cases 

 of diphtheria in your state. 



Diphtheria. This disease is caused by bacteria which grow 

 rapidly in the throat and form a false membrane there. But 

 the most serious results come from the toxin, thrown off by the 

 bacteria, which get into the blood and not only cause suffering 

 and fever but also may have very serious after-effects on various 

 body organs. As diphtheria is a throat disease, it may easily be 

 conveyed from one person to another by the droplet method of 

 infection. 



Other diseases spread through mouth spray. Influenza, pneu- 

 monia, whooping cough, and certain kinds of colds, and many 

 of the so-called children's diseases, are caused by bacteria or other 

 microscopic organisms. Nearly all are spread by the " droplet 

 method " of infection. In our army during the World War, 

 influenza, coupled with pneumonia, was responsible for fourteen 

 times as many deaths as were caused by shells and poison gases. 

 This disease is periodically epidemic, the last bad outbreak pre- 

 vious to this being in 1889. Influenza is apparently spread largely 

 by human carriers, or people who have a slight attack but are 

 capable of passing the disease on in its most serious form. 



Project. Use the report on infectious diseases, United States Public 

 Health Reports, or your State Department of Health bulletin to deter- 

 mine the decrease in typhoid in your state for the past ten years. 



Typhoid fever. Typhoid fever, not many years ago, was one 

 of the most common germ diseases in this country and Europe. 

 Today it is one of the less important of the communicable diseases. 

 Typhoid bacilli multiply very rapidly in the intestine and are 

 passed off from the body with the excreta from the food tube. 

 If these bacilli get into the water supply of a town, an epidemic of 

 typhoid will result. In one early epidemic in this country there 

 were 5000 cases of typhoid in a city of only 30,000 inhabitants. 



