52 REPORT OF THE BACTERIOLOGIST OF THD 
require oxygen in some form and give off carbon dioxide, which 
is partly responsible for the bulging of the cans. Sugar in 
moderate quantities is especially useful to those growing in canned 
goods since it furnishes them with oxygen. 
The character of the decomposition depends partly upon the 
nature of the original compounds and partly upon the form into 
which the particular germ breaks them in extracting the por- 
tion desired as food. The germs causing the swelling of peas 
break up the sugar in such a way as to produce a large amount 
of gas and a small amount of acid. The ones producing souring 
in peas break up the sugar so as to leave a large amount of acid 
and little or no gas. 
BACTERIA ARE OF DIFFERENT KINDS. 
In objects which are only about 1-25000 of an inch wide and a 
few times longer than broad there is but a limited amount of 
information to be derived with a microscope. However some 
forms are round like miniature peas while others are rod-like. 
The latter differ slightly in plumpness and in the position and 
appearance of their spores. The spores are very resistant bodies 
formed within the cells and capable of starting growth anew at 
some later time. The growing cells are killed by any ordinary 
amount of cooking but the spores often survive and cause trouble. 
The bacteria which are capable of destroying canned goods are 
not only of different species but, what is of more importance to 
the canners, the spores of different species are capable of with- 
standing different amounts of heating. As a result of this, - 
canners who have been processing successfully at a low tempera- 
ture for a number of seasons suddenly find themselves in trouble 
when a more resistant species gets into the cans. 
Until outbreaks of swelling and souring of a given vegetable 
have been studied in a number of factories we will not be able to 
draw safe general conclusions as to what temperature can be 
absolutely relied upon to keep the given vegetable under all con- 
ditions. While these facts are being ascertained the safest prac- 
tical plan will be to give the cans the amount of heating required 
to kill the most resistant species known to trouble the particular 
vegetable and as much more as the vegetable will stand without 
injury to its commercial quality. 
