BACTERIOLOGY IN A NUTSHELL. 



Decay of 

 Animals. 



Where 

 Oxygen is 

 Obtained. 



The same thing happens in decay of dead 

 plants and animals. In decomposition of ani- 

 mals 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 preparation made for mixing with the 

 soil and the atmosphere. Whatever of the de- 

 cayed 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, to 

 be returned to the elements from which it 

 came, again to be used in the formation of 

 something else in the various processes of 

 Nature. So plant and vegetable and animal 

 life is renewed and sustained in a great 

 measure through 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 

 activities of bacteria. 



We inhale from the atmosphere oxygen, 

 which is absolutely necessary for the sustenance 

 of animal 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 king- 



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