2/8 AGRICULTURAL BACTERIOLOGY. 



water that bacteria are unable to grow in them. There is little 

 difficulty in preserving these for an indefinite length of time. 

 This is true of most grains. Nature herself, at the end of the 

 growing season, extracts the water from these seeds, leaving 

 the comparatively dry mass to remain over the period of rest 

 until the growing time comes again. There is no difficulty in 

 preserving such foods from bacterial attack. 



But some of the food material which we wish to preserve 

 contains a large amount of water and cannot be so easily dis- 

 posed of on the farm. Where the amount of water is high, 

 the farmer must find some means of protecting the food from 

 bacterial action. This is accomplished in a variety of ways. 



In the problem of the relation of bacteria to farm products 

 we have, therefore, two different topics to consider : (i) The 

 agency of bacteria and fermentations in preparing the crop. 

 (2) The methods of protecting the crop from the attack of 

 mischievous organisms. To a certain extent the two subjects 

 overlap, since in several cases the very methods adopted for 

 preserving the material furnished it with flavors, or other char- 

 acters, which distinctly add to its value. These will be con- 

 sidered in the present chapter, leaving for the next chapter 

 those subjects connected simply with the preservation of farm 

 products. 



I. 'ACETIC ACID FERMENTATION. VINEGAR-MAKING. 



This fermentation is one of the very greatest importance. 

 In the first place it is the basis of a large industry of vinegar- 

 making, which is carried on extensively in all countries. It 

 also forms the foundation of the great industry of pickle-manu- 

 facturing, which makes it possible to find a use for large quan- 

 tities of vegetable products that would otherwise be a waste 

 product, thus furnishing a market for the product of many 

 a cucumber farm. But, besides these extensive applications 

 of the acetic fermentation, it is found on a smaller scale 



