12 



increase owing to a too low temperature and the presence 

 of a more numerous and active competitor, comes into a 

 more favourable temperature for development, activity and 

 multiplication. 



We know, then, some of the influences of temperature. 



]X'ow some bacteria can only live when they have plenty of 

 air plenty of free oxygen, and in this respect they do not 

 differ from other living things. They are termed Aerobic 

 bacteria. Anaerobic bacteria, on the other hand, can live 

 only in the absence of free oxygen not that they can 

 entirely dispense with this life-sustaining element, 

 but because they have the power of obtaining oxygen 

 by breaking up organic matter, which contains a certain 

 proportion of oxygen. Then there are bacteria known as 

 Facultative Aerobic bacteria and Facultative Anaerobic 

 1 ;icteria, so called because the}' appear to possess the faculty 

 of adapting themselves to any condition between the two 

 extremes of when there is a plentiful supply of oxygen 

 present and when there is a complete absence of free 

 oxygen. 



We therefore find that bacteria are the cause of 

 fermentation and putrefaction ; that certain temperatures 

 render some bacteria inactive ; and that the amount of 

 oxygen to them obtainable regulates the amount and kind 

 of fermentation which is likely to take place. 



When fermentation is taking place heat is evolved, as, 

 for instance, when a heap of stable manure is first made 

 up. The rise in temperature is due to chemical changes 

 which are taking place in the mass, owing to the presence 

 and action of bacteria. The chief action observable is one 

 of oxidation. If oxidation is going on at a great rate, and 

 that is when air is being freely admitted, the temperature 

 will be higher than when oxidation is limited. In fact, if 

 nir were totally excluded, the rise in temperature would be 

 very slight. 



We have mentioned roughly, and of necessity simply, the 

 fundamental principles applicable to the successful making 

 of silage. 



Having learned something of the nature of bacteria, let 

 11 . see what happens when green fodder is heaped up in 

 large quantities. 



The miscroscopic organisms which are found on nil 

 vegetation now find the conditions favourable to their 

 attack. The fodder, now lifeless, can no longer resist the 

 attack, and the tissues become food for these germs. 

 Different kinds are always present. Yeast-like ones convert 

 the starchy and sweet matter into alcoholic compounds, 

 others, taking up the work, convert the alcohol into vinegar. 

 ome produce lactic, others butyric acid. Other bacteria 

 convert the albuminoid constituents into complex nitre,- 



