FERMENTATION AND ALCOHOL 49 



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ir. Alcohol disappears very rapidly after being taken 



into the body. 

 12. Alcohol takes water from the lining of the mouth 



and produces thirst. 



DEMONSTRATIONS 



18. Show fermentation by setting aside a bottle containing a little 

 molasses in water. In a few days bubbles will rise, showing that fer- 

 mentation has begun. Add a little yeast to another bottleful, and 

 notice that fermentation begins within a few hours. Boil another 

 bottleful and at once cork it tightly, and notice that it does not change. 

 Explain that the first bottleful started with few germs and so fermenta- 

 tion at first was slow. The second had many and fermentation began 

 at once. In the third the yeast germs were destroyed and so no fer- 

 mentation took place. 



19. Set aside a bottle of weak molasses and water for a week or two. 

 Notice that fermentation goes on but that the liquid now tastes sour, 

 for it has become vinegar. 



20. Soak a yeast cake in water for a few hours and examine a tiny 

 drop under the microscope with a power of at least 200 diameters. 

 Notice the small oval cells, from the edges of which tiny cells seem to 

 be budding. These are yeast cells. In the same specimen starch 

 grains will appear as much larger irregular bodies of a shape depending 

 upon the kind of grain used in making the yeast. 



21. Procure some alcohol. Notice its sharp odor and taste. Show 

 that it will dissolve and remove grease from the hands. Explain that 

 in the arts, it is used to dissolve oils, resins, and such substances as 

 water will not dissolve. Procure some wood spirits and contrast its 

 odor and taste with that of common alcohol. Show that it, too, 

 dissolves grease. 



22. Pour some alcohol upon the white of an egg. Notice that the 

 alcohol coagulates it and turns it white. 



23. Place a small piece of tender meat in a bottle of alcohol for 

 a. day or two. Notice that it turns whitish in color and becomes 

 shriveled, hard, and dry. Explain that the alcohol takes away the 

 coloring matter of the meat, and 'also coagulates the albumin much in 

 the same way as hemlock bark tans leather. Explain how alcohol pre- 

 serves substances in this way. 



ov. PHYSIOL. 4 



