PRESERVATION OF DRYING 255 
terials, the food could be preserved indefinitely. But these organ- 
isms or their spores are so abundant everywhere that this is im- 
possible, except by hermetical sealing. Some foods, however, are 
thus protected. Fruits have a certain amount of protection 
against the molds that cause their decay, since their uninjured 
skins resist their entrance. The smooth hard skin of many fruits 
is impervious to the mycelium of the mold, though it can readily 
force its way in through a bruise or crack into the softer substance 
within. Hence the bruised apple decays quickly. Wiping the 
skin of fruit clean and dry will protect it for a long time from decay. 
The wiping cleans off most of the mold spores that may be on the 
skin, and the drying of the skin leaves no moisture in which the 
few spores left can germinate. If moisture condenses on the skin, 
as when the fruit is taken from a cold room into a warm one, decay 
is sure to follow, since this moisture starts the germination of the 
spores into a mycelium and the latter is pretty sure to find some 
place in the skin through which it can pass. Once inside the skin, 
it grows rapidly through the soft pulp and the fruit is soon spoiled. 
The preservation of fruit is, thus, a matter of keeping it dry, at a 
low temperature, and with an unbroken skin. Even the wrapping 
of fruit in paper materially aids in its keeping, since the paper 
absorbs the moisture that collects on the skin. 
PRESERVATION BY DRYING 
The simplest means of preventing the growth of bacteria in 
food products is by drying. Anything that can be dried without 
destroying its value as a food can in this way be effectually pro- 
tected against bacterial action. No method of preserving food 
products is so universally used as this, and none other is so 
effective. 
Grains.—In the preservation of the valuable cereal products 
nature herself adopts this plan and, when the grain is ripening, the 
large amount of water which was present in the green seed disap- 
pears, leaving the ripened grain, somewhat shriveled, perhaps, but 
