PROBLEM 4. How We Atte?npt to Stop the Spread of Disease 357 



14. Describe the four stages in the life history of the mosquito. What 

 are three methods of exterminating mosquitoes? 



15. Explain why mosquito extermination has not proved as successful in 

 stamping out yellow fever as was at first hoped. 



16. Besides the microorganisms, what other group of organisms cause 

 disease? What are the two ways of fighting these diseases? 



17. Describe the appearance of the hookworm. Tell how it enters the 

 body, by what route it travels through the body, and what harm it 

 does. How is it spread to the next victim? What measures are being 

 taken in our country to stop the disease? 



18. How do we get trichinosis? Where in us does the worm settle? How 

 may the disease be avoided? 



19. Describe the appearance and habits of the tapeworm. In which ani- 

 mals do the larval (young) stages of the tapeworm live? How does 

 the worm leave the host? 



20. Why can we hope soon to know more about the spread of disease 

 and about epidemics? 



Exercises 



1. What are some of the functions of a health department? List as 

 many of the functions as you can think of. Glancing through paragraph 

 titles in this problem may suggest some that have not occurred to you. 

 Reports prepared by different individuals or committees can then be 

 read to the whole class. 



2. (a) Why does drinking water carry the germs of intestinal diseases 

 but rarely carry diphtheria germs? (b) Towns sometimes pipe sewage 

 to the ocean near oyster beds. Explain why this is dangerous to the health 

 of persons both in the town and in other places. 



3. (a) How could there have been any cases of typhoid in Albany 

 after the water was filtered? (b) How^ can you explain the fact that 

 oysters, celery, lettuce, and ice cream may sometimes be the means of 

 spreading the germs of typhoid fever? (c) Since typhoid germs cannot 

 form spores what advice was probably given the people of Albany before 

 the water was filtered? 



4. Using a sterile dropper, dilute a little pasteurized milk with about 

 10 times the amount of sterile distilled water in a sterile test tube. Shake 

 well. Spread several drops over the surface of a sterile Petri dish contain- 

 ing nutrient agar. Using a second Petri dish, repeat, using milk that was 

 opened for use a day or two ago. Put several drops of distilled water on a 

 third as a further control. Place the dishes in a warm place. Examine after 

 48 hours. Take careful notes. What have you learned? 



5. Scientific discoveries are often the work of many workers. Show 

 how the discovery of the cause of malaria was international. Discuss two 

 other examples of scientific discoveries that were built on the work of 

 others. 



