XII. 



CEOPS 255 



the stack, an open conical structure composed of wooden scant- 

 lings meeting at a point. The stack is then built round and above this. 

 These methods depend for their efficiency not upon checking the heat 

 production, as the first one does, but upon the removal of the evolved 

 heat by circulation of air. 



The odour of hay, upon which its palatability largely depends, 

 is probably due partly to the products of fermentation, among which 

 compound ethers are probably present, and partly to coumarin, 



/~tTJ . /^TT 



C 9 H 6 2 or C 6 H 4 / ' - which occurs in woodruff (A sperulaodorata), 



^O . CO, 



in Bokhara clover (Melilotus), in sweet-scented vernal grass (Antho- 

 xanthum odoratum), and probably in many other plants. 



Coumarin is a crystalline solid with a characteristic odour (that of 

 new-mown hay), is slightly soluble in water, and very soluble in alcohol. 

 Its odour becomes very pronounced when plants containing it are 

 dried. 



Ensilage or Silage is made by preserving green fodder in a closely 

 compacted condition so as to prevent access of air as much as possible 

 and so hinder the various fermentative changes from proceeding be- 

 yond a certain stage. Originally, all silos consisted of pits or buildings 

 of stone or wood, in which the materials could be stored and subjected 

 to high pressure. It is now a common practice to simply stack the 

 fodder in the green state, treading or pressing it down as much as 

 possible, and finally weighting it with stones or earth. In all cases 

 the outside of the silo, where air has access, becomes so rotten as to 

 be useless, but the amount of waste is not very great. 



The changes which occur in the silo are in many respects similar 

 to those in the stack, but fermentation is limited in a different 

 manner by air exclusion, while in a stack it is chiefly from lack of 

 sufficient moisture. Consequently, it is found that the relative pro- 

 gress of different organisms is different in the two cases. Moreover 

 in a silo, the predominant character of the fermentation, and conse- 

 quently of the silage, depends largely upon the management. If the 

 silo be made slowly, so that a considerable amount of heating may 

 occur before the weighting expels the air, the temperature rises so 

 high (up to 55 or 60) that the bacteria which produce acids (e.g., 

 acetic, lactic and butyric acids) are destroyed. The resulting pro- 

 duct is then known as " sweet " silage. If the silo be built with little 

 delay and compressed at once, the temperature does not rise so high, 

 and the acetic, lactic and other acid-producing bacteria are not killed, 

 but produce their characteristic products, thus leading to the forma- 

 tion of " sour " silage. 



The changes in composition which fodder undergoes during fer- 

 mentation in a silo, lead to a loss of carbohydrates, partly as gaseous 

 products and partly by conversion into insoluble " fibre ". Except by 

 mechanical loss, say by juices running from the silo, the mineral 

 matter undergoes no change ; the albuminoids are slightly lessened, 

 probably by conversion into amides, and even into ammonium salts. 



