EXPERIMENTS 95 



as a drug and not as a food. It paralyzes the higher 

 nerve centres which are responsible for our ideas of right 

 and wrong, as well as those which control the larger 

 movements of the body. As a result, the person who 

 comes under its influence ceases to be normal in his 

 thoughts or actions. 1 



EXPERIMENTS AND DEMONSTRATIONS 



Materials: Samples of water; yeast cake; iodine solution 

 (p. 83); microscope with powers up to 450 diameters; tall 

 glass bottles. 



1) Fill a tall glass with water and allow to settle. Pour off 

 carefully so as to leave sediment undisturbed. Stucty a drop of 

 the sediment under microscope. 



2) Boil water for 10 minutes. Cool and taste. 



3) Shake up some of the boiled water in 2) in a large clean 

 bottle, % of which is filled with air. Repeat several times at 

 intervals of a few minutes, and compare with the taste of 2). 



4) If your water supply is from well or cistern, draw a 

 diagram of premises to show possible sources of contamination. 



If it is from a general town supply, describe its source and 

 the precautions taken to insure its purity. 



5) Dissolve a small piece of yeast cake in a few drops of 

 water, a) Examine a drop of the fluid under microscope and 

 make drawings of the cells present. 



b) Add a small drop of iodine solution and again examine. 



1 For a more complete discussion of the effects of alcohol, see 

 Chapter XXVI. 



