260 DECOMPOSITION 



chemical and energy changes taking place in decomposi- 

 tion are the same as those which take place in the bodies 

 of the living organisms which produced the materials 

 acted upon. Thus digestion and decomposition, the 

 metabolic processes involved in respiration and certain 

 fermentations, and the post mortem changes immedi- 

 ately following death have many features in common, 

 the most significant of which is enzymic action. (See 

 Chap. VII.) 



Kinds of Decomposition. — (a) Digestion. This 

 topic, mentioned here because it is a part of the general 

 subject, has been discussed elsewhere (Chap. VII) at 

 sufficient length. It is accomplished by enzyms which act 

 upon various sorts of organic matter. 



(b) Autolysis. This is the name given to decomposi- 

 tion taking place in bodies immediately after death, and 

 is entirely independent of invading organisms. It is 

 accomplished by enzyms formed by the organism previous 

 to its death. It may be more than suspected that some 

 at least of these changes taking place after death are 

 the same as those taking place before death. Autolytic 

 changes undoubtedly take place in the bodies of plants 

 as well as animals, although even less is known about 

 autolysis in plants than in animals. 



(c) Metabolism for Energy Release. In both plants 

 and animals the use of food as fuel results in its decom- 

 position and the liberation or release of energy. The car- 

 bohydrates and other non-nitrogenous compounds are 

 oxidized directly or indirectly in the metabolic processes, 

 the oxidation, when completed, resulting in the produc- 

 tion of CO2 and H2O, with the liberation of energy. The 

 energy liberated may be immediately used for work in 

 the form of muscular or other movement, locomotion, 

 etc. ; but if not used for work, it will escape as heat. 



(d) Protein Metabolism. The complex nitrogenous 

 compounds of carbon known collectively as proteins — 

 constituents of living protoplasm — are converted in 



