ORGANIC MATTER in 



keep their bodies as long as they ar© useful, but just as soon as life 

 becomes extinct they are dragged off to the bacterial bonfire so 

 that the elements composing them can serve other plants and 

 animals. How marvelous! Growing in water teeming with bac- 

 teria is a nalced mass of protoplasm, an ameba, during life, it is 

 not only unattacked by bacteria but actually feeds upon them. But 

 let death come, and the ameba then serves as food for the bac- 

 teria. Growing in the soil are plants thriving upon the by-prod- 

 ucts produced by bacteria. Something happens, the plants die, and 

 bacteria thrive upon them. From the moment of birth, man is 

 surrounded by saprophytes. They are on the skin, in the secretions 

 of the nose, mouth, and eyes, they fairly swarm in the alimentary 

 tract, and probably do no harm; but let death come and nature's 

 wrecking crew, the bacteria, become so active in pulling the body 

 to pieces that if we are any distance from a friend at the time of 

 death we must hasten to obtain even a last fond glimpse of the 

 body of the dear one. 



The speed with which decomposition proceeds varies with the 

 nature of the original product and the microorganisms taking part. 

 It is also modified by the presence or absence of air. When de- 

 composed in the absence of air there are produced many ill-smell- 

 ing products. This is usually spoken of as putrefaction. Where 

 the organic matter is broken down by bacteria in the presence of 

 air we refer to it as decay. 



In the process of decay the carbon and hydrogen are liberated 

 as carbon dioxid, methane, water, and other volatile products with 

 the result that the carbon in the soil tends to fall off relatively 

 to the nitrogen and the carbon-nitrogen ratio which in the orig- 

 inal plant material is about 40, is reduced in the soil to 10. This 

 carbon-nitrogen ratio varies with climatic conditions, also with 

 soil type and previous treatment. Lawes and Gilbert give the 

 following carbon-nitrogen ratio in the organic matter of different 

 soils: 



Cereal roots and stubble 43*° 



Leguminous stubble ^23.0 



Dung 18.0 



