INTERRELATIONS OF PLANTS AND ANIMALS 131 



with water, stopper, and set it aside in a warm place. Note 

 the odor after 10 or 12 hours. 



Note. Any odor will surely indicate the .presence of bacteria, 

 although they may be present without an odor. 



2. Rinse another recently emptied milk bottle with cold 

 water, then with boiling water, and finally scald it by boiling 

 it in a pot of water for 5 minutes. Drain it well, stopper it, 

 and set it aside as the first one. Note odor as before. 



Conclusions. 1. What care should be observed with vessels 

 that have contained milk ? 



2. What is the effect of high temperature on bacteria in milk ? 



Questions 



1. Why coat eggs with paraffin or soluble glass (sodium 

 silicate) ? 



2. Why are hams and bacon smoked ? 



3. How is it that such an animal as the mammoth has been 

 found entire and in a good state of preservation in Siberia ? 



4. Explain the principle of sour and sweet pickles. 



5. Explain the advantage of the following method of can- 

 ning fruits. Put fruit and a sufficient amount of sugar to suit 

 in jars, cover them loosely, arid set them in an oven for heat- 

 ing or in a boiler with a few inches of water and boil the 

 water for a half hour. See that the boiler is closed, also that 

 the jars do not stand directly on the bottom of the boiler. 

 Place a cloth under them, or some strips of wood, to prevent 

 breakage. 



6. Why should pasteurized milk be cooled at once ? 



7. What is the principle of drying foods to make them keep ? 



8. Explain the Italian proverb, "Where the sun does not 

 come the doctor does." 



Special Reports 



1 . The importance of decay. 



2. Pasteurization. 



3. The importance of wholesome milk and how to attain it. 



