ECONOMIC IMPORTANCE OF FUNGI 305 
series of operations intended primarily to kill all germs of 
bacteria and fungi. The sterilized fruit is then sealed 
from the air and from access of other germs while it is 
still hot. The "keeping" of canned goods depends upon 
the successful exclusion of every living spore or other 
germ. If goods preserved in tin cans have been im- 
perfectly sterilized the gases produced by fermentation 
will exert a pressure upon the can from the inside, often 
strong enough to cause a bulging of the ends. 
COLD STORAGE 
Just as canning has for its object the preservation of 
vegetable or animal tissues by killing the germs with 
heat, so cold storage accomplishes the same end by means 
of extreme cold. Most germs remain inactive below a 
certain temperature, which may be readily ascertained 
by experiment. The spoiling of eggs is caused by the 
presence within the egg of a germ-" flora," which lives 
upon the yolk and white, producing by its life proc- 
esses, the noxious gases of stale eggs. At certain low 
temperatures most of the life-processes of the germs 
are either stopped entirely, or greatly retarded. In the 
colonial days of America, and later, it was common for 
dwellers on farms and in villages to preserve meat by 
burying a quantity of it in the snow during the winter 
season a primitive cold storage. During cold storage, 
however, certain chemical changes take place in the 
preserved tissue, due to enzyme action. As a result 
there is a limit to the period that food can be kept in cold 
storage without deteriorating. All cold-storage plants 
and refrigerator cars are evidence of the fact that our 
own lives are profoundly affected by the existence and 
activity of microscopic forms of plant life. 
