CHAPTER 2 



HUMAN AND ANIMAL WASTES 



A7td a place shalt thou have without the camf, whither thou shalt 

 go forth abroad: and a spade shalt thou have with thy weapons ; 

 and it shall he, when thou sittest abroad, thou shalt dig therewith, 

 and sh-alt afterward cover that which cometh from thee. — 

 Deuteronomy 2^:1^ and 14. 



Human and animal excreta and other waste products, which are or fre- 

 quently become both offensive and dangerous to public health, sooner 

 or later find their way into the soil and water basins. The soil also re- 

 ceives the many residues of growing crops that are annually left on the 

 land, together with the waste materials of the farm and the home (439, 

 922). These wastes contain substances partly digested by man and ani- 

 mals, and their metabolic waste products, as well as freshly synthesized 

 material in the form of microbial cells. The microbial population of 

 such waste materials comprises agents of digestion, some microbes that 

 are present accidentally, and some that possess the capacity of causing 

 human, animal, and plant diseases. 



These waste materials do not remain long in an unaltered form and 

 do not accumulate in or on the surface of the soil or in water basins j 

 otherwise both soil and water long ago would have been rendered un- 

 sightly, disagreeable bodies, which man would not dare to tread upon 

 or enter. On the contrary, the soil and the water are capable of di- 

 gesting all these cast-off materials and of completely destroying their 

 undesirable characteristics. Through all past ages, the waste products of 

 plant and animal life have disappeared, whereas the soil and the water 

 in the rivers, lakes, and seas have remained essentially the same, except 

 under very special conditions such as those that brought about the pro- 

 duction of peat in water-saturated basins and, in past geological ages, 

 the formation of coal. The capacity of soil and water to destroy these of- 

 fensive wastes is due entirely to the microorganisms that inhabit the 

 substrates. The important ultimate products of destruction are am- 

 monia, carbon dioxide, and water j often hydrogen and methane are 



