CHAPTER XXIII 

 HOW WE FIGHT BACTERIAL DISEASES 



Problems: What is the incubation period of a disease and what 

 is its significance? 



Why is quarantine necessary? 



What is natural immunity f 



What is active immunity ? What is passive immunity f 



What are antitoxins and how are they used? 



What are vaccines and what do they do ? 



Laboratory Suggestions 



Laboratory study of vital statistics. Construction of graphs of certain infec- 

 tious diseases. 



Field work. Visit to a local board of health or to a hospital to learn how- 

 certain tests are made and how protection against disease is obtained. 



Reasons for Quarantine. — We all know that when a person 

 has a communicable disease, the doctor, acting under orders of the 

 local board of health, puts the patient and sometimes the entire 

 family under quarantine. Since this often seems needless, espe- 

 cially if one has a mild attack of the disease, we ought to know the 

 reason underlying such action. Communicable diseases become 

 epidemic if they are not controlled. Measles, for example, is a dis- 

 ease easily passed from one person to another. It is especially 

 communicable among children, one of whom may have a very 

 light case but may pass the germs to some one else who will have 

 a severe attack of it. Scarlet fever, colds, and influenza are other 

 diseases which are readily spread and may become epidemic. 



Since this is true, the reason for the isolation of the patient 

 becomes evident. And every one should be unselfish enough to 

 see this and to cooperate with the health authorities for the common 

 good of the community. 



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