SUMMARY 269 



to live. The activities of these bacteria result in the pro- 

 duction of enzyms which carry on hydrolysis — the split- 

 ting of proteins into simpler organic nitrogenous com- 

 pounds, like the albumoses and peptones — which are 

 themselves broken down by other enzyms to animo-acids. 

 The putrefying carcass, furthermore, bloats from the pro- 

 duction of gaseous substances within the cavities of the 

 body, and the series of decompositions includes the pro- 

 duction of those offensive odors which indicate to us the 

 presence of a dead animal. As the body of the animal 

 breaks down mechanically as well as chemically, the final 

 products of decay are liberated, escaping into the air or 

 washing into the soil, thus becoming once more available 

 as raw materials for the manufacture of food by plants. 



Summary. — From the illustrations which have been 

 employed it should be clear that the decomposition of 

 carbohydrates and fatty substances consists of successive 

 phases. These consist in processes resembling those which 

 go on in the plant or animal body and properly termed 

 digestion. The products of digestion, whether inside the 

 living body or in excreta or in lifeless remains, may 

 be oxidized, thus liberating energy which may be 

 used by the active organisms. The final result in every 

 case so far investigated is the liberation of the energy 

 originally stored by photosynthesis or by other metaboHc 

 processes, and the setting free of the C in the form 

 of CO2 and H in the form of H2O. Thus through all the 

 multifarious transformations of substance there has been 

 no loss of material or of energy. The free energy of the 

 sunlight has been stored up in organic compounds as po- 

 tential energy, to be liberated either by the organism 

 which stored the energy or by others in their various 

 activities. 



The proteins are broken down in the animal body 

 itself by digestion, etc., and in the lifeless remains of ani- 

 mals and plants, by the aid of other organisms, mainly 

 bacteria and fungi. Here also the substances and the 



