82 THE INVISIBLE WORLD 



In the former case the particles of the dough are 

 packed solidly together and baked in that condi- 

 tion, with nothing to push them apart. The bread 

 is therefore solid. It could not be otherwise. 



In the latter case the yeast introduced is liter- 

 ally full of living microbes. Their services make 

 the bread light. As soon as these beings find them- 

 selves in the dough, they begin to subsist on the 

 sugar of the flour, and grow, and multiply with 

 great rapidity, until they occupy every part of the 

 dough. In consuming the sugar of the dough, they 

 decompose and digest it. The decomposition prod- 

 ucts are carbon dioxide gas and alcohol. The 

 entire mass of dough is thus saturated with 

 this gas and alcohol. The gas is expansive, 

 and, by its force, pushes apart all the par- 

 ticles of the dough, leaving interspaces be- 

 tween them. As the dough thus occupies more 

 room, it is said to " rise." The rising is noth- 

 ing more or less than the separating one from an- 

 other all the particles of the dough, thus expand- 

 ing it into a larger volume. This is what renders 

 the bread light and spongy, all owing to the 

 friendly work of the microbes. 



A great service this to the entire world. All 

 the bread used in every home, which is made light, 

 palatable and nourishing by using baker's yeast, is 

 the gift of the microbe. This being conferring such 

 infinite good is yet but about the ^Vir part of an 

 inch in diameter. This means that the yeast is 

 wet, that the microbe is full grown, Fig. 55, and 



