THE SOLID NITROGENOUS WASTES 267 



wastes are thus broken down to their original status of 

 raw materials which are restored to the soil, and the 

 energy involved in their manufacture is once more 

 released. 



The Solid Nitrogenous Wastes, consisting of pro- 

 teins, amino-acids, and the intermediate products, under- 

 go successive decompositions by the corresponding bac- 

 teria which are nourished thereby, ammonia and CO2 

 being the end products. In the course of such decomposi- 

 tions offensive odors may be produced. Hence the name 

 putrefaction is applied to them. But whether the process 

 results in the production of evil smells or not, the results 

 are the same, the release of energy and the production of 

 simpler and simpler compounds until the residue finally 

 appears as ammonia and various sulphates and phos- 

 phates. 



Putrefaction is brought about chiefly by bacteria, 

 aided to some extent by fungi. The number of kinds of 

 bacteria accomplishing these changes is very large, and 

 the exact chemical reactions produced by each are as yet 

 only imperfectly known. While bacteria requiring free 

 oxygen (aerobes) are able to decompose proteins, this 

 ability is shared by certain species of bacteria (e.g., Bacil- 

 lus botulinus) which can be active only in the absence of 

 free oxygen (anaerobes). Many of the former can carry 

 the process to completion, giving rise to CO2 and am- 

 monia (NH3). The anaerobic bacteria cannot usually 

 carry decompositions so far, and the two sorts form 

 intermediate products which are more or less different. 



Putrefying Substances are of inany sorts and from 

 many sources — meat, milk, eggs, seeds, are familiar 

 materials which putrefy. Compounds which undergo 

 actual putrefaction are proteins and their primary de- 

 rivatives. From these proteins, mainly by bacterial 

 activities, though fungi may also take part, the amino- 

 acids are formed, which may in turn be broken down to 

 still simpler compounds. 



