NATURE OF FERMENTED DRINKS 83 



123. Bacteria, the Active Agents of Fermentation. The 



myriads of living creatures that play this part as active 

 agents in the process of fermentation are grouped under 

 the family, or generic, name of bacteria. 



The words germs, microbes, and microorganisms are often 

 used with the same meaning as the term "bacteria." 



Bacteria are very low forms of plant life, of which 

 there are many varieties. They are roughly divided into 

 groups, according as they are spherical, rodlike, or spiral 

 in shape. It is now known that a large number of species 

 of bacteria exist, but that some forms which have been 

 described are simply stages in the life history of other 

 forms. 



It is impossible for us to realize how small these agents 

 of fermentation are. Some of the rod-shaped are from 

 a twelve-thousandth to an eight -thousandth of an inch 

 long, and average about a fifty-thousandth of an inch in 

 diameter. It has been calculated that two hundred and 

 fifty millions of minute organisms would not weigh more 

 than one milligram (Sees. 419-426). 



124. Mold. To this great family of bacteria belong 

 certain low forms of plant life familiar as mold. This is a 

 low form of fungous growth which is often seen upon decay- 

 ing wood or old leather. It is this fine, furlike coating 

 which spoils our bread and cheese, causes our sauce to 

 sour, and our fruit to rot. 



The work of some kinds of molds may be apparent to 

 the eye, as in the growths that form on old leather and 

 on stale bread and cheese. The work of other kinds of 

 molds goes on unseen, as when acids are formed in stewed 

 fruits. One kind of mold devours our preserves; another 

 turns our bread sour. One kind is nourished at the 



