FERMENTATION AND GERM DISEASES 63 



organism, and we speak of this kind of fermentation as due 

 to an organized ferment. 



Later in this chapter, another group of organisms, the bac- 

 teria, are discussed and their intense fermentative powers are 

 pointed out. Being organisms, they too would be termed 

 organized ferments. While this designation is a convenient 

 one in some ways, there is valid objection to its use. It is not 

 the organisms themselves which are the ferments, but rather 

 the substances which they produce. But usage has, as a 

 rule, been that which is adopted in this text. 



Fermentation of Starch. The change of starch to sugar 

 is a very simple one and is due to the union of starch with a 

 little water, as follows: 



CeHioOs + H 2 O 

 Starch Water Sugar 



If we mix starch with water alone, we get no such result; 

 but when we mix starch and water with saliva, the combina- 

 tion of starch with water begins, and sugar is formed. This 

 may continue until the starch is all converted into sugar. 

 If we boil the saliva it entirely loses this power; yet, if we 

 study saliva with a microscope we find no living bodies in it 

 corresponding to the yeast plant. Nevertheless, there is some- 

 thing in the saliva that provokes this change. That something 

 can be separated from the saliva, and when so separated it 

 appears as a white, structureless powder. It does not grow, 

 multiply or increase like yeast during the fermentation pro- 

 cesses. Since it is not alive it cannot be called an organism, 

 and we speak of it as an unorganized ferment; it is more 

 commonly called an enzyme. It is clearly a ferment but quite 

 different from the yeast ferment. Moreover, when this enzyme 

 converts starch into sugar, the starch and some water arc 

 used up, but the enzyme remains unaltered. 



