118 PHYSIOLOGY AND NATIONAL NEEDS 



been published in the American Journal of Agricul- 

 tural Research * by Messrs . Bailey and Gur j ar . These 

 authorities accept the view " that the phenomenon 

 known as respiration is responsible for the heat 

 energy released in a mass of damp grain." Un- 

 fortunately botanists use the term respiration in 

 an extraordinarily wide sense, including thereunder 

 all the complex and varied processes of destructive 

 metabolism, so that it becomes impossible to dis- 

 tinguish between respiration and fermentation. 

 Messrs. Bailey and Gur jar, however, clearly exclude 

 microbic fermentation as a cause of the heating of 

 grain. In the same paper they tell us that " sponta- 

 neous heating in damp grain is occasioned by the 

 biological oxidation of dextrose and similar sugars, 

 chiefly in the germ or embryo of the kernel." The 

 term " biological oxidation " is perhaps less objec- 

 tionable than " respiration," though it may well 

 be questioned whether biological oxidation can be 

 distinguished from chemical oxidation. 



Apart from theoretical considerations, however, 

 the paper referred to contains much valuable in- 

 formation as to the conditions under which " heat- 

 ing ' ' takes place. The most important determining 

 factor is obviously moisture. The increase in the 

 rate of the so-called "respiration" is slow and 

 gradual until the moisture content of the grain 

 reaches some 13-1 4- 5 per cent, after which it becomes 



1 VoL xii. No. 11, Washington, March 18, 1918. 



