88 * THE RESPIRATION OF APPLES. 



destruction of matter in the cells much like the destruction 

 of wood in a stove, and the rate at which this destruction 

 goes on can be measured by determining the amount of 

 carbonic acid that is breathed out in a given length of 

 time. 



In animals, under usual conditions, the food which they 

 eat makes good the losses produced by respiration. An 

 animal, however, may live without food for some time, dur- 

 ing which period it still breathes in oxygen and breathes 

 out carbonic acid and water, but it steadily loses weight and 

 grows thin in flesh because there is a steady destruction of 

 cell material with no food to replace it. 



Fruit, after having been picked from the tree, is in the 

 condition of the starving animal. Its cells still keep up 

 respiration with nothing in the way of food to make good 

 the losses produced by the action. Since apples and other 

 fruits have no body heat to maintain, the breathing process 

 is not so active as in animals, and they may last months 

 after being picked from the tree. Yet there is a steady, 

 continuous loss in weight as the weeks go by, although the 

 fruit is sound and firm. 



For example, fruit put in cold storage Nov. 13 and 

 weighed at intervals of two months had lost as follows : 



January 2, 0.33 per cent. March 5, 2.34 per cent. 



May 6, 3.60 per cent. July 1, 4.71 per cent. 



That the shrinkage in weight is due to respiration and 

 not to simple drying out of the water is shown by the 

 practically constant percentages of water and dry matter, 

 since if the solid material was not destroyed it should grad- 

 ually increase in proportion while the water would de- 

 crease. Results proving this point are here given. 



A lot of Baldwin apples were set aside in October and a 

 few of them analyzed at intervals. 



October 24, water, 85.45; dry matter, 14.55. 



October 31, water, 8.') -41; dry matter, 14. .59. 



November 21, water, 85.23; dry matter, 14.77. 



November 29, water, 85.02; dry matter, 14.98. 



December 27, water, 85.56; dry matter, 14.44. 



April 20, water, 86.19; dry matter, 13.81. 



Respiration is partly a chemical reaction and in apples, 

 like most chemical reactions in the laboratory, it grows 

 more rapid as the fruit becomes warmer, and is slowed 

 down when the fruit is cooled. If two sets of experiments 

 were carried out as described in a previous paragraph, one 

 set in a refrigerator, and the other in a warm room, it 

 would be easily seen at the end of four or five days that 

 the warm room had caused the larger amount of respiration. 



