HOW WE GET DISEASES 463 



race. A very large proportion of these diseases might have been 

 prevented if people were educated sufficiently to take the proper 

 precautions to prevent the spreading of bacteria. Such precau- 

 tions might have saved the lives of some 3,000,000 people yearly 

 in Europe and America. Tuberculosis, typhoid fever, bubonic 

 plague, diphtheria, pneumonia, blood poisoning, and a score of 

 other diseases ought not to exist. But within the last decade, 

 due to the sacrifices and discoveries of men in medical science, the 

 control of a number of bacterial diseases has been made possible. 

 It is estimated, for example, that with the cooperation of the people, 

 diphtheria might have been stamped out in New York state by the 

 end of the year 1930. That this has not happened is due certainly 

 to the number of uninformed people who will not or do not know 

 how to cooperate with the medical authorities. A large amount 

 of the present misery of this world might be prevented, and this 

 earth made cleaner, better, and safer, by the cooperation of young 

 people in carrying out and enforcing health regulations. 



Practical Exercise 3. Make a table to show all the ways in which bacteria 

 may cause disease and give an example under each heading. 



Self-Testing Exercise 



Bacteria cause almost (1) (2) (3) of the 



(4) of the human race. Many of these might have been 



(5) if people would (6) with the medical authori- 

 ties. Bacteria cause disease either by forming (7), releasing 



(8), or by (9) on the (10), thus breaking 



them down. 



PROBLEM III. HOW DO WE GET BACTERIAL DISEASES? 



How we get diseases. Bacteria causing infectious diseases enter 

 the body either by the mouth, nose, or other body openings, or 

 through a break in the skin. They may be carried by means of 

 air, food, or water, but are more often transmitted directly from 

 the person who has the disease to a well person. They may be 

 acquired through personal contact, as kissing; in a spray of 

 tiny droplets which are expelled into the air as a person talks; 



