A GRADED COURSE OF NATURE-STUDY 471 



Physiology and Hygiene : Organic impurities in well- 

 water or other drinking water. Sources of contamination 

 — surface drainage into well, sewage contamination in river 

 supply. Danger of drinking such ' water. Diseases that 

 may come from it — typhoid especially. (262, 263, etc., 209, 

 208, 381, 368, 372, 379, etc.) Simple talk about bacteria. 

 Note putridity of peas in water after a few days. Exposed 

 boiled potato kept moist under glass will develop a growth 

 of bacteria. Place some peas in a bottle of water, boil 

 for some time, and seal. Set aside and observe if decay 

 sets in. If well done the bottle should remain clear. Briefly 

 tell about sterilization. Refer to reason for boiling fruit 

 for canning. Discuss iiltration. How is an ordinary water 

 filter made?* (262, 263, etc.) Simple talks on conta- 

 gion, and prevention of disease. Keep hands and face 

 clean. Clean finger nails, do not spit, do not cough in 

 people's faces, do not put in your mouth what others have 

 had in theirs, do not suck the pencil, do not put coins or 

 anything but the proper things in the mouth. Turning leaves 

 by wetting the finger is not only bad for the book, but is 

 dangerous to the health, for others may have done the same 

 before. Discuss the need of cleanliness in the kitchen, 

 cellar, refrigerator, the floors of home and school, and the 

 streets and backyards. Refer to the evils of dust. Car- 

 pets vs. rugs. Mopping vs. sweeping and "dusting." (209, 

 208, 274, 373, 368a, etc., 375, 387.) Why do we keep 

 people in quarantine? Is it right? (References as last.) 

 House ventilation * — home and school. (251, 250, 368a, 

 etc. ; 262, etc. ; 386, 387.) Need for it. What happens to the 

 air we breathe. Test breath for carbon dioxide. In a simple 

 way discuss the source of this COj. Refer to the food we 



