PRODUCTION OF HEAT IN FERMENTATION 



263 



enclosed in the center of each. Support the boxes properly. 

 Germinate enough seeds of Pisum to fill both boxes. When the 

 roots are a centimeter long, fill one of the boxes with seedlings 

 which have been killed by boil- 

 ing water and then placed in a 

 separate germinator to cool. 

 Fill the second box with normal 

 seedlings. Both lots must offer 

 the same degree of moisture. 

 Place the apparatus where it may 

 not receive sunlight and both 

 lots of seeds will receive the 

 same temperature from the out- 

 side. Lay a piece of moistened 

 filter paper over the top of the 

 seedlings. Note the height of 

 the columns of colored spirits 

 in the arms of the tube at inter- 

 vals of an hour (Fig. 1 29). 



FlG. 129. Measurement of heat pro- 

 duced in respiration, by differential ther- 

 mometer, a, cardboard box containing 

 growing seedlings, b, box containing 

 germinated seedlings killed by immer- 

 sion in hot water and then cooled. The 

 expansion of the vapor in the bulb in the 

 living seedlings has driven the column 

 of spirits down in the arm below and up 

 into the other arm of the thermometer, 

 which has not been similarly affected. 

 After Belzung. 



333. Production of Heat in 

 Fermentation. Pour 250 cc. of 

 Pasteur's solution into an Erlen- 

 meyer flask, and a similar 

 amount of distilled water in a 

 second. Place 5 g. compressed 

 yeast in each flask, and close the 

 mouth of each with cotton wool through which passes a delicate 

 thermometer so that the bulb is immersed in the culture solution. 

 Place both flasks in a steady temperature of about 22 to 25 

 C. Compare the temperature of the two flasks after fermenta- 

 tion has set up. This experiment may also be performed with 

 the differential thermometer. Secure two rubber stops of a 

 diameter greater than the bulbs. Make perforations the size of 

 the thermometer tubes, and a cut from one side into the per- 

 forations. Place around the tubes, and fit to them large tubes, 



