PUTREFACTION AND DECAY 101 



more or less anaerobic conditions ; where an abundant 

 supply of air is maintained, as in porous soil or loosely 

 compacted compost and manure heaps, the substances 

 possessing an objectionable odour are either not pro- 

 duced at all, or are rapidly oxidized into odourless 

 compounds, in which case the organic material is said 

 to decay. The end-products of the processes of putre- 

 faction and decay are the same, the proteins being 

 finally broken down into simple gaseous bodies such 

 as methane, carbon dioxide, hydrogen, ammonia, and 

 sulphuretted hydrogen, which diffuse into the atmosphere 

 or are washed into the soil by rain. 



A great amount of investigation has been carried on 

 to determine the character of the changes involved in 

 the putrefaction process not only in nitrogenous materials 

 exposed to the air, but in food constituents passing 

 through the alimentary canal of animals. Experiments 

 have been made with pure cultures of bacteria upon 

 single proteins, and the general nature of putrefactive 

 degradation is fairly clear. In the first stages the pro- 

 cess is similar to that which takes place in proteins 

 under the influence of trypsin or boiling acids, albumoses, 

 peptones, and amino-acids being formed. The splitting, 

 however, proceeds in such a manner that only small 

 amounts of the two former kinds of compounds are met 

 with at any stage of the decomposition. The enzyme 

 trypsin is unable to bring about further change in the 

 amino-acids which it produces, but the putrefactive 

 bacteria can utilize these in their nutritive processes, and 

 carry the degradation much further. From some of the 

 amino-acids ammonia is eliminated, and the correspond- 

 ing acids without nitrogen are obtained, in the same 

 manner as if they were decomposed by alkalis or 



