314 AGRICULTURAL BACTERIOLOGY. 



freshly mown grass is piled in heaps from 10 to 13 ft. high, 

 the mass being trodden down as tightly as possible to prevent 

 the admission of air. In these heaps a spontaneous fermenta- 

 tion soon sets in which produces a rapid heating of the mass, 

 a rise in temperature being sometimes noticeable in twelve 

 hours. The temperature rises rapidly and is watched with a 

 thermometer. When it rises to about 158 F., which occurs 

 commonly in from forty-eight to sixty hours, the heaps are 

 opened and spread out in thin layers to the air. The heat in 

 the hay now rapidly dries the product and with a single turning 

 it is ready for storing. The hay thus prepared develops an aro- 

 matic odor which ordinary sun-dried hay does not possess, 

 and is for this reason somewhat superior. 



The nature of this fermentation is simply a matter of conjec- 

 ture. It has, like other fermentations, been attributed to the 

 action of bacteria, the very great rise in temperature being at- 

 tributed to certain species of bacteria which are known to live 

 at high temperatures. But this hardly seems probable. It is 

 found that if these heaps are not opened to the air when the tem- 

 perature reaches about 158, there is a still greater heating of 

 the mass, and finally the whole may ignite by spontaneous com- 

 bustion. Such a phenomenon certainly cannot be produced 

 by bacterial action, since not even the heat-loving bacteria 

 (tJicnnopliilous bacteria) are able to produce such high heat as 

 to cause their own death. It is, therefore, much more 

 probable that the phenomenon here involved is one of the 

 chemical fermentations due, either to respiratory changes, or to 

 enzyme-like bodies, which bacteriologists are now learning 

 play such an important part in fermentations hitherto at- 

 tributed to bacteria. 



Brown Hay. Another method of preparing hay is ex- 

 tremely common in countries where the rains are too fre- 

 quent to make possible the drying by the two methods above 

 mentioned. This is frequently employed in rainy districts 



