RESPIRATORY SYSTEM 355 



carriage. They are all preventable diseases. The duty 

 of preventing their spread rests with each one of us. 



Vaccination for smallpox was discovered by Jenner 

 in 1796. Since that time the public has gradually 

 become convinced of the advantages of this, as well as 

 other methods of protection against that one-time ter- 

 rible disease. In the following table notice the effect 

 this has had upon the prevalence of the disease. Com- 

 pare with this the death rate due to impure air dis- 

 eases and it will be evident that we are facing a great 

 problem, but one which each of us can share in solving. 



CHICAGO'S MORTALITY FOR THE YEAR 1910* 



CAUSE NUMBER OF DEATHS 



Smallpox 1 



Influenza . 146 



Bronchitis 171 



Tuberculosis of Lungs 3,366 



Pneumonia 3,526 



Questions 



1. Why do all living things need air ? 



2. What is meant by internal respiration? By 

 external respiration ? 



3. Name the parts of the respiratory tract begin- 

 ning with the nasal passages. Briefly describe the 

 structure of each. 



4. Why should we avoid mouth breathing ? 



5. What are the chief features of the larynx? 



6. How is sound produced? 



7. What is the pleura? What are its functions? 



8. Explain how the thorax is enlarged. 



From Report of the Department of Health of the City of 

 Chicago for the years 1907-1910. 



