266 THE PRESERVATION OF FOOD PRODUCTS 
another farm product. It is no longer necessary for the farmer 
to depend upon his own market, but, by the aid of canning, his 
market may be the world, open to him the whole twelve months 
of the year. The canning industry makes it possible for the 
farmer to become a specialist, where it was impossible a few 
years ago. He may raise green corn, or tomatoes, or straw- 
berries as abundantly as he pleases, and whatever he cannot find 
an immediate market for may be preserved for a later season by 
the process of canning. It is well for the agriculturist to learn 
that in farming, as in all other industries, it is the specialist who 
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Fig 49——Three species of bacteria causing the spoiling of canned corn 
(Prescott and Underwood) 
succeeds, and that the proper utilization of the process of canning 
is one of the means of making a special product upon a farm yield 
proper returns. Canning makes possible an intensive farming, 
undreamed of a few years ago. 
The present condition of the canning industry has been 
reached only after years of experience, accompanied with many 
failures and losses. Whole shipments have sometimes been 
ruined by “swelling,” which means that the cans swell out from 
the force of the putrefying gases forming within. The failure 
to appreciate the difficulty of killing bacterial spores has caused 
great losses of canned corn, peas, and beans, as well as tomatoes. 
It must be recognized that, for successful canning, every spore 
must be killed; for if a single one be left alive in the middle of the 
can, the product is sure to spoil (Fig. 49). The slowness with 
