FERMENTATION AND PUTREFACTION. 177 



In making aerated bread, carbonated water is used instead 

 of yeast, with the same effect, and with the advantage that 

 there is no loss of starch, and no products of decomposition 

 are left in the bread.* 



There are many other vegetable-ferments, most of which 

 are, however, unpleasant; some produce " maladies " in beer, 

 some acidity, some putrefaction, according to their various 

 ways of feeding; but though each has a flavour peculiar to 

 itself, the character of all is essentially the same. When we 

 like their effect, we call it "fermentation," when we do not 

 like it, we call it "putrefaction." 



The name of bacteria (Fig. 8) is given to a large variety 

 of these organisms, which, though much lower down in the 

 scale of life than the mildew on decayed wood, are yet nearly 

 allied to the fungi. They are the agents of all putrefaction, 

 and though no microscope is powerful enough to detect their 

 germs, they abound in all the moist places of the earth, and 

 being so inconceivably minute that a grain of pollen is 

 gigantic in comparison, are not only easily lifted into the air 

 by the wind, on a dry day, but are even drawn up with the 

 water as it evaporates. 



It is evident that all putrefaction is caused by them ; for 

 milk, meat, &c., which remain perfectly sweet for an indefi- 



* The use of the word ' ' leaven " to denote a good influence seems strangely 

 inappropriate in the face of these facts and the circumstance that " leaven 

 in the inspired writings is always taken as the type of naughtiness and sin " 

 The most prominent idea connected with leaven is that of corruption but 

 this idea was not peculiar to the Jews. The priest of Jupiter was forbidden 

 to touch flour mixed with leaven, and the Romans sometimes used the word 

 ' ' fermentation " for corruption. ' ' The radical force of the word matzzoth 

 unleavened is sweetness or purity. ; ' Smiths Dictionary. 



