BACTERIOLOGY IN A NUTSHELL. 
Decay of 
Animals. 
Where 
Oxygen is 
Obtained. 
tree has been attacked by bacteria, it drops to 
pieces as a yellowish brown deposit, to mix with 
dead leaves and sink into the soil as a fertilizer 
to promote the growth of healthy plants and trees 
that inhabit the forest. 
The same thing happens in decay of dead 
plants and animals. In decomposition of animals 
saprophytes play a still more important part, as 
it is by their agency alone that the work on every 
part of such bodies is accomplished, and the prep¬ 
aration made for mixing with the soil and the 
atmosphere. Whatever of the decayed substance 
of tree and plant and animal is not of use as a 
fertilizer is disseminated in the form of gases to 
be taken up by the air. So plant and vegetable 
and animal life are renewed and sustained in a 
great measure by the fertilization of the soil by 
decomposition of dead plants and vegetables and 
animals, and by the gases they disseminate, none 
of which would come to pass without the activ¬ 
ities. of bacteria. 
We inhale from the atmosphere oxygen, which 
is absolutely necessary for the sustenance of ani¬ 
mal life, and which is thrown off for our use 
from growing plants and trees and other forms 
of vegetable life. We exhale carbonic acid gas, 
or “carbon dioxide,” which, together with the 
influences of the sun and the rain, is necessary 
for the growth and sustenance of trees and plants 
and vegetables. This is one way, among others, 
in which the animal kingdom is necessary to the 
vegetable kingdom and vice versa, the plant 
and vegetable world giving off oxygen for use of 
the animal world, and the animal world in its turn 
supplying the plant and vegetable world with 
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