20 STATE BOARD OF AGRICULTURE. 



In ordinary fermentations we find micro-organisms at work clianging 

 starch to sugar, sugar to alcohol and carbonic gas, and alcohol to acetic 

 acid, the acid of vinegar. Farther, you are all acquainted with the 

 usual process of changing sweet milk into sour milk, or to be more 

 exact, of changing sugar of milk to lactic acid. These changes are 

 brought about by the direct action of micro-organisms. Moreover, what 

 is known as putrefaction is attributed lo micro-organisms also. A piece 

 of meal, i? placed on the surface of the ground; in a few days it will have 

 completfiy disappeared. You note in your wood lot the accumuUtion 

 of heaps of dead leaves in the fall time, and before another season has 

 passed these leaves have lost their organic structure and nothing but a 

 black, loose dirt remains, mixed with a few remnants of leaves, to 

 indicate the origin of the dirt. You place a straw stack in your barn- 

 yard, and each ^^ear, although you make no use of it, notices a marked 

 decrease in its size, and eventually the straw, with its well marked 

 outlines, lies a heap of Mack soil. In the manure heap the same thing 

 is noticeable. Allowed to stand, in a few years there will be none. 

 Whetlier it is the transformation of starch through sugar into alcohol, 

 or milk sugar into lactic acid, or the destruction of a piece of meat on 

 the surface of the ground, or the disappearance of the leaves in the 

 wood lot, or the reduction of the straw stack or heap of manure, the 

 principle involved in all of these actions is the same, and all of them 

 are brought about through the instrumentality of micro-organisms. 



The starch is more complex in its structure than alco^hol and carbonic 

 acid gas, and meat and leaves are far more com])lex than the resulting 

 dirt which they produce. Remove the micro-organisms, the starch would 

 remain as starch and Ihe meat and leaves as meat and leaves. The 

 action of micro-organisms seems to be that of reducing these complex 

 materials to simples. The plant feeds upon the simple constituents of 

 the soil and in turn feeds the animal which produces the meat; that is. 

 the simple substances of the soil have been transformed into the com- 

 plex substances composing the meat through the instrumentality of the 

 plant. As the material leaves the soil it gradually becomes more com- 

 plex till it has reached its most complex form, we will say, and then, 

 after life has fled, it again returns to the simple elements of the soil 

 through the agency of micro-organisms. 



Picture to yourself an atom of nitrogen associated with less than a 

 dozen atoms in the soil to form some soil compound, and then regard 

 it in the animal body, associated perhaps with hundreds to form the 

 substance of a muscle. Farther, imagine that atom of nitrogen in its 

 complex association reduced to the simple combinations of the soil, or 

 even free nitrogen of the air, tlien you shall be able to see that which 

 it has taken the plant and animal to accomplish, has been undone by 

 these simple micro-organisms. 



The above action of micro-organisms we will call destructive or an- 

 alytical. 



On the other hand a constructive or synthetic process is possible. 



If, for instance, the germ of consumption be placed in a purely min- 

 eral solution composed of simple compounds, this germ will utilize this 

 solution in its growth and development in the manufacture of products 

 of a poisonous and complex nature. That is just like the plant and 

 animal. It is able to take into its body certain simple bodies and froni 

 them create highly complex bodies. 



