PRESERVATION BY CANNING. 247 
quantities could be raised. For example: before the beginning of 
tomato canning, only a very small crop could be utilized; but the 
opening of this canning industry has entirely changed the conditions, 
and now great tracts of land can be devoted to raising this delicacy, 
thus opening to the farmer an entirely new outlet for his crop. The 
same is true of many another farm product. It is no longer neces- 
sary 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- 
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M 
FIG. 50. Three species of bacteria causing the spoiling of canned corn 
(Prescott and Underwood}. 
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 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 
