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 CHAPTER X

BACTERIA AND SANITATION

Experiment 1. Yeast Plants.—With a microscope examine a drop from a glass of water in which you have washed grapes or apples (Fig. 129).

Experiment 2. Fermentation.—Put a tablespoonful of sugar into this water and set the glass in a warm place for a day or two. Do you see any bubbles of gas? Have the odor and taste changed? Does the microscope show that the yeast plants are now more abundant? By fermentation, or the growth of yeast in sugar, sugar is changed into carbon dioxid, a gas, and alcohol, a liquid.

Experiment 3. A Sanitary Map.—Construct a sanitary map of the community. Indicate houses where consumption, typhoid fever, or other transmissible diseases have occurred, with number of cases. Mark location of stagnant waters where mosquitoes breed, mark garbage dumps, unclean streets. Suggest where improvements may be made in drainage, dust, noises, sunshine, shade, etc.

magnified 200 diameters, or 40,000 areas). Yeast plants multiply by budding. Notice small cells growing on larger and older ones.

Bacteria, or microbes, the smallest living things, are visible only under a microscope of high power. (See "Plant Biology," p. 182.) They obtain food either from dead tissue or from degenerate tissue of living plants and