MICROOBGANISMS AND HUMAN WELFARE 43 



body are ever ready to produce. In the case of many of the 

 contagious diseases, like scarlet fever or smallpox, these 

 antitoxins remain for a considerable time in the blood to 

 make us immune against a second attack. The white cor- 

 puscles, too, are a sort of cavalry troop, ready to pounce upon 

 the bacteria and either devour them or carry them off from 

 the body (Fig. 12, A). An optimistic view of life and free- 

 dom from worry are undoubtedly very important factors in 

 keeping the body in a state of vigorous health. 



41. Topics for biolo^ composition.' — Optional Library 

 Work. Consult the local health authorities, AUen's "Civics and 

 Health," Bulletins of U. S. Department of Agriculture, New Inter- 

 national or other Encyclopedia, and other sources, and prepare in 

 your notebook a composition on one or more of the following 

 topics: — 



1. The Work of the Board of Health. 



2. The Work of the Tenement House Commission. 



3. How a City May Be Kept Clean. 



4. A Visit to a Model Dairy. 



5. City Milk Inspection. 



6. A Hygienic House. 



7. Helpful Bacteria. 



8. City Playgrounds and Parks : Their Use and Abuse. 



9. How the Study of Bacteria Can Help Us in Our Homes. 



10. Sleeping in the Open Air. 



11. A Visit to Ellis Island: How the Commission Cares for 

 Immigrants. 



12. The Responsibility of the Individual for Public Health. 



13. An Ideal School Infirmary. 



14. The Work of the Consumers' League. 



15. Methods of Sewage Disposal. 



16. The City Water Supply. 



1 The authors are indebted to Miss Edith Read of the Morris 

 High School for the following list of composition topics. 



