very large, it is insufficient to cause rapid fermentation, and if we
depended upon wild yeast for bread raising, the result would not be to
our liking.

When our remote ancestors saved a pinch of dough as leaven for the
next baking, they were actually cultivating yeast, although they did
not know it. The reserved portion served as a favorable breeding place
to the yeast plants within it; they grew and reproduced amazingly, and
became so numerous, that the small mass of old dough in which they
were gathered served to leaven the entire batch at the next baking.

As soon as man learned that yeast plants caused fermentation in
liquors and bread, he realized that it would be to his advantage to
cultivate yeast and to add it to bread and to plant juices rather than
to depend upon accidental and slow fermentation from wild yeast.
Shortly after the discovery of yeast in the nineteenth century, man
commenced his attempt to cultivate the tiny organisms. Their
microscopic size added greatly to his trouble, and it was only after
years of careful and tedious investigation that he was able to perfect
the commercial yeast cakes and yeast brews universally used by bakers
and brewers. The well-known compressed yeast cake is simply a mass of
live and vigorous yeast plants, embedded in a soft, soggy material,
and ready to grow and multiply as soon as they are placed under proper
conditions of heat, moisture, and food. Seeds which remain on our
shelves do not germinate, but those which are planted in the soil do;
so it is with the yeast plants. While in the cake they are as lifeless
as the seed; when placed in dough, or fruit juice, or grain water,
they grow and multiply and cause fermentation.

CHAPTER XXII

BLEACHING

217. The beauty and the commercial value of uncolored fabrics depend
upon the purity and perfection of their whiteness; a man's white
collar and a woman's white waist must be pure white, without the
slightest tinge of color. But all natural fabrics, whether they come
from plants, like cotton and linen, or from animals, like wool and
silk, contain more or less coloring matter, which impairs the
whiteness. This coloring not only detracts from the appearance of
fabrics which are to be worn uncolored, but it seriously interferes
with the action of dyes, and at times plays the dyer strange tricks.

Natural fibers, moreover, are difficult to spin and weave unless some
softening material such as wax or resin is ru