BACTERIA IN NATURAL PROCESSES. 121 



of the fertile soil appears to resolve itself into a 

 proper handling of bacteria. These organisms 

 have stocked his soil in the first place. They 

 convert all of his compost heap wastes into simple 

 bodies, some of which are changed into plant 

 foods, while others are at the same time lost. 

 Lastly, they may be made to reclaim this lost 

 nitrogen, and the farmer, so soon as he has 

 requisite knowledge of these facts, will be able 

 to keep within his control the supply of this im- 

 portant element. The continued fertility of the 

 soil is thus a gift from the bacteria. 



BACTERIA AS SOURCES OF TROUBLE TO THE 

 FARMER. 



While the topics already considered comprise 

 the most important factors in agricultural bacte- 

 riology, the farmer's relations to bacteria do 

 not end here. These organisms come incidentally 

 into his life in many ways. They are not always 

 his aids as they are in most of the instances thus 

 far cited. They produce disease in his cattle, as 

 will be noticed in the next chapter. Bacteria are 

 agents of decomposition, and they are just as 

 likely to decompose material which the farmer 

 wishes to preserve as they are to decompose ma- 

 terial which the farmer desires to undergo the 

 process of decay. They are as ready to attack 

 his fruits and vegetables as to ripen his cream. 

 The skin of fruits and vegetables is a moderately 

 good protection of the interior from the attack 

 of bacteria; but if the skin be broken in any 

 place, bacteria get in and cause decay, and to 

 prevent it the farmer uses a cold cellar. The 

 bacteria prevent the farmer from preserving 



