45 
;FOR WAGGONER’S BIOLOGY 
I. Fill each of eight test tubes one-third full of the solution. 
Allow No. 1 to stand in an oven at 90° F. (about 32° C.), No. 2, 
in a room at about 65° F., and No. 3, in a refrigerator at about 
45° F. Let the three tubes remain under these conditions for 48 
hours or until No. 1 becomes cloudy. Close Nos. 4, 5, 6, 7, and 8 
with cotton plugs. Place No. 4 in water held at 60° C. for 5 minutes; 
No. 5 in water held at 70° C. for five minutes; No. 6 in water at 
80° C. for five minutes; No. 7 in water held at 90° C. for five 
minutes; and No. 8 in boiling water for five minutes. Then allow 
these five to stand in the oven at 90° F. (about 32° C.). What 
general difference do you observe in these eight tubes after forty- 
eight hours? What does a cloudy appearance indicate? What is 
the use of the hay? Why was the cool wash water added in the 
beginning? Why were the tubes of the last group closed with 
cotton? (If no oven and refrigerator are available for this experi¬ 
ment, approximate results may be obtained in winter by placing 
the tubes in the furnace room and in a cold room. 
II. What do the first three tubes show in regard to the effect of 
heat upon the growth of bacteria? Which clouded first? Why? 
Explain the differences observed in the last group of tubes. What 
is the effect of high temperature upon bacteria? Why do sub¬ 
stances decay more rapidly in warm than in cooler weather? In 
warm weather, why does food keep better in the ice chest than out 
of it? Why does surface water become stagnant in warm weather? 
EXERCISE 48 
ORGANIC MATTER IN WATER 
I. Procure samples of distilled, faucet, well, cistern, pond, and 
dirty surface water, placing each in a separate bottle. Fill each 
bottle one-half full and label it. Shake the bottles before studying 
their contents. Note any odor which is present. Explain the 
presence of such odors, if possible. Cork the bottles and place in 
an oven held at 90° F. (or in a furnace room) for two or more days. 
At the end of this period examine the samples again. Note the 
