32O AGRICULTURAL CHEMISTRY 



uisite, as a ferment which acts upon one class of bodies is 

 incapable, unaided, of acting upon others ; for example, 

 the peptic ferment is incapable of changing starch to 

 soluble forms. When a substance is freed from all fer- 

 ments and is protected from outside sources of contami- 

 nation, it is in a sterile condition. Many forms of fer- 

 mentation are produced by the spores of organized fer- 

 ments gaining access to a material along with dust particles 

 carried in the air. In the preservation of food, a knowl- 

 edge of the conditions requisite for fermentation is made 

 use of. The products formed by ferments are numerous, 

 as there are ferment bodies capable of acting upon all forms 

 of organic matter. Some of the ferments assist in the 

 digestion of food and in the preparation of food products, 

 while others take an important part in every-day life 

 affairs, and in agriculture as in the liberation of plant 

 food. The growth of plants, the preparation of foods, 

 and their digestion, and the manufacture of food products 

 all depend largely upon fermentation. 



441. Soil Ferments. In the growth of plants, fer- 

 ments take an important part, both in the preparation of 

 the plant food and in the chemical changes which take 

 place within the plant. Disintegration of the mineral 

 food of the soil is assisted by ferment action. The nitroge- 

 nous food of the plant is all prepared in the soil by fer- 

 ments. The subject of soil ferments is briefly considered 

 in the " Chemistry of Soils and Fertilizers." 



442. Ferments in Seeds. In the seeds of plants, par- 

 ticularly matured grains, there are a number of ferments 

 which take an important part in the process of germina- 



