HYGROSCOPICITY 



'53 



and there is the water which they hold only as living structures, 

 the water of vitality. The chemist, when producing by 

 synthesis organic vegetable matter, would allow the atmosphere 

 to supply the water of hygroscopicity, whilst he himself in his 

 creative role would have to supply the water of vitality. This 

 in a sense is very much what a baker does when he adds water 

 to his flour in making bread. As shown below, bread behaves 

 like fresh plant-tissues when dried in air and when desiccated 

 by heat. The water it regains from the air after heating is 

 the water originally existing in the flour as supplied by the 

 miller, and the water it does not gain back is what the baker 

 put into it. 



EXPERIMENTS BY THE AUTHOR ON IOO-GRAIN SAMPLES OF BREAD IN 

 ILLUSTRATION OF BERTHELOT'S " PRINCIPLE OF REVERSIBILITY." 



Divided into small squares, the bread occupied about six days in reaching a stable 

 weight in air before being placed in the oven, where it was kept for i hours. Three to 

 four days were passed in acquiring a stable weight after the oven test. 



When we come to apply the test of experiment to this The same 

 principle as it affects seeds, we get the same indications. The fnistrated in 

 simple experiment of drying a fresh seed first under ordinary 

 air-conditions, then in the oven at 100 to no C., and after- seed, 

 wards allowing it to remain exposed to the air for a few days 

 until it assumes a stable weight, supplies results that make the 



