Heating of Hay 453 



all unlikely, therefore, that these organisms, capable 

 of growing at comparatively high temperatures, play a 

 direct role in the changes that occur at elevated tem- 

 peratures in large masses of vegetable materials. 



The process of heating, as it occurs in moist hay, may, 

 therefore, be described as follows: The soluble substances 

 that pass out of the moist material serve as food for a 

 host of bacteria. The chemical changes thus occasioned, 

 and perhaps also the respiration of the vegetable cells 

 that are still living, lead to temperature elevation. The 

 heat accumulated in the mass of hay destroys the less 

 resistant forms, and, as the temperature rises higher and 

 higher, even the most resistant species are killed off. 

 Hay infusions, inoculated with particles of hay so heated, 

 at times remain sterile, a fact that tends to prove that 

 the process may amount to self-sterilization. 



Brown hay. Bacterial activities, in so far as they 

 are at all concerned in the temperature changes that 

 occur in the curing of hay, are utilized in some localities 

 for the preparation of so-called brown hay. In this in- 

 stance, the wilted grass is arranged in large, well-com- 

 pacted piles, and is protected from the rain. The de- 

 velopment of heat becomes manifest at the end of two 

 or three days, when the mass begins to steam. It retains 

 its high temperature for from eight to fourteen days, as 

 may be readily shown by placing a thermometer in a 

 metal pipe driven into the heated material. 



After the steaming subsides, the hay is allowed to 

 remain undisturbed ^or several weeks longer. It is then 

 of a pale to a dark brown color, rather firm and dry, 

 and somewhat aromatic. As chemical analyses have 



