"That depends on the amount of carbonic gas which is developed. When it first raises the gas forces its way through the dough irregularly, and by then working it the gas is broken up and distributed evenly, so that if the mass is allowed to stand after the second working every part of it will be leavened. When it is then put into the oven, the heat at first causes a more rapid expansion, or raising, of the dough, and as the heat increases, fermentation is stopped, and the baking process sets the dough. The result is tiny little holes throughout the bread, where the gases were."
"But why do they use yeast if it can be done without?"
"Because it makes the raising process easier, and more positive."
"Is it the carbonic acid which makes some bread sour?"
"Yes; sour bread results if the fermentation is continued too long."
