298 GENERAL SCIENCE 



QUESTIONS 



1. Why are not all mosquitoes dangerous? 



2. How are you able to tell the difference between the mosquito 

 which causes malaria and the mosquito which is harmless? 



3. What methods should be used to prevent mosquitoes from 

 breeding and carrying disease? 



4. Why has vaccination practically exterminated smallpox? 



5. Why is it wrong to say that hot weather causes dogs to have 

 rabies? 



6. Why should a dog who has bitten a person be confined for 

 nine or ten days? 



7. What should be done immediately to a person who has been 

 bitten by a dog? 



DISEASES CAUSED BY BACTERIA 



Colds. A "cold" is not a proper name tor the disease which 

 we call the " common cold " for the simple reason that effects of 

 cold or any other outside influence alone are powerless to produce 

 the condition known by that name. Arctic explorers who go into 

 a region where it is impossible for germs to live never have colds 

 due to exposure to cold winds. They may have a great deal of 

 mucus from the membrane of the nose and throat, but they do not 

 suffer from pains in the back and joints, and other general discom- 

 forts which the "cold" brings to us. It is also known concerning 

 Arctic explorers who make a long stay in regions where there are 

 few bacteria, that the secretions of the mucous membrane gradually 

 lose their germicidal power to kill the bacteria of "cold," so that 

 on their return to more temperate latitudes, consequently to places 

 where there are many germs, they suffer severely from attacks of 

 "colds" or catarrh. The bacteria which produce "colds" live 

 continually in the mucous membrane. There is always flowing 

 from the mucous membrane a secretion of mucus, the function 

 of which is to protect the body. The air passing from outside 

 must pass through this mucus. For this reason the dust particles 

 of the air, bearing bacteria, mold, etc., are deposited on the walls 

 of the respiratory passages, so that under normal condtions but 

 little dust and few bacteria reach the lungs. 



