1392.) Some Uses of Bacteria. 991 
starches or the cellulose that is in the body of the dead tree. 
Nevertheless, the plants do succeed in getting hold of this 
food, and it is through the agency of these bacteria that we 
are speaking of this morning that they do it. Just as soon as 
the body of an animal or plant dies, the bacteria get into it, 
begin to grow in it, decomposing it, and pulling it to pieces. 
They pull the starch to pieces, they pull the sugar to pieces, 
and albumens and fats share the same destruction. Little by 
little they take those ‘compounds which plants cannot feed 
upon, and, by shaking them to pieces, bring them down to 
simple combinations which plants can feed upon. 
Of special importance is one particular kind of organism 
known as “the nitrifying organism,” which produces nitric 
acid. Plants as I have said, cannot feed upon such things as 
albumen. The putrefying bacteria can decompose albumen 
and break it up into certain simple compounds, but ordinary 
putrefying bacteria are not able to break that albumen down 
far enough for plants to get hold of it. Plants have got to 
live upon such things as nitrates and salts of nitric acid. 
Now, there is one sort of bacteria living in the soil which gets 
hold of the albuminous compounds and forms nitric acid. 
This is the nitrifying organism, and the nitrification is the 
last stage in the decomposition process by which an albu- 
minoid is converted into a condition in which plants can get 
hold of it. One practical application of this you are all 
familiar with in the ripening of fertilizers. You know that 
green manure is of absolutely or of practically no use as a 
fertilizer on your fields. You know that it must first stand 
for a while and ripen, or “rot,” as you call it. Now, what is 
taking place in that fertilizer while it is ripening? Simply 
the series of changes that have been mentioned. That fertil- 
izer contains chemical compounds of a high degree of com- 
plexity, compounds that the plants cannot feed upon ; they 
are too highly complex for plants to use as food. _ Bacteria, 
however, get into that heap and begin to grow in it; and, as 
the fertilizer becomes ripened, these high chemical compounds 
are pulled to pieces, they become converted into simpler 
position products, and eventually, if the ripening be 
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