266 MAN'S IMPROVEMENT OF HIS ENVIRONMENT 



connected with the sewer system of the city. If such toilets are 

 not screened from flies, report the matter at once to your board of 

 health. Why are the latter toilets a particular menace to public 

 health? (See Civic Biology, page 224.) 



7. Locate on your map any pushcarts, stands, or stores in which 

 vegetables or fruit are exposed for sale. Indicate if they are 

 obeying the laws of your sanitary code with reference to the ex- 

 posure of goods for sale. Why is it a wise law that requires goods 

 exposed for sale to be covered ? Is there any spitting in the streets 

 in this locality? Are there any other ways in which germs might 

 get in the dust of the street? How might bacteria be carried 

 from the street surface to the food exposed? 



8. Find any public fountains having drinking cups; bubble 

 fountains. Which is more hygienic? Why? 



9. Locate any hotels or other places having common roller 

 towels. Why are common towels a danger to public health? 

 What can you do to prevent the use of the public towel in your 

 neighborhood ? 



10. Locate any other factors that might in your opinion affect 

 public health in your neighborhood. Factories belching forth 

 smoke or acid fumes, tall buildings shutting out light, old tenement 

 houses, and filthy conditions of street are among such factors. 



Conclusion. — 1. Is my neighborhood a good one in which to 

 live? Give reasons. 



2. How may I help to better the conditions that affect public 

 health in my locality? 



Problem 238 : To determine the bacterial content of different 

 grades of milk. 



Materials. — Different grades of milk, sterile bulb pipette, 

 sterile test tubes, absorbent cotton, sterile Petri dishes containing 

 agar culture media. 



Method. — Procure milk from different sources and of different 

 grades if in a large city. Be sure to include milk dipped from a 

 can in some store. Have samples of milk collected kept under 

 identical conditions and be sure that the milk has been collected 

 from the milk companies at the same time. Then treat each 



