436 



FOODS 



The ancient Egyptians knew that if flour was mixed with 

 water and left in a warm place it would soon become 

 porous ; and that if pieces of this porous dough were put into 



FIGURE 136 



other dough, they would make this dough become porous 

 more quickly. These pieces of dough were called leaven, 

 and the leavened bread of the ancients was made in this 

 way. Even to-day in some countries this method is fol- 

 lowed. The Romans 

 sometimes used a leaven 

 made out of grape juice 

 and millet. In these 

 methods, the wild yeast 

 plants which exist al- 

 most everywhere in the 

 air found a favorable 



lodging in the prepared substance, and by their growth 

 and activities " raised " the bread. Later, methods were 

 devised for cultivating the yeast plants, and the making 

 of " raised " bread became common. 



YEAST PLANTS 



