444 AGRICULTURAL AND INDUSTRIAL BACTERIOLOGY 



human beings ; they should as far as possible be protected 

 from flies and vermin which might carry disease organisms 

 present to the food of man ; and particular care should be 

 used not to allow them to gain access to drinking supply. 



Probably in most rural communities the privy vault is 

 most used for this purpose. Wherever there is any danger 

 of contamination of wells, it should be water tight and 

 arranged so that it is possible to clean at intervals. The 

 addition of lime or bleaching powder in some cases will 

 reduce odors. Proper covers should be provided so that flies 

 cannot gain access and breed in the excreta. 



The modern farm is rapidly becoming equipped with the 

 same sanitary conveniences as the city home. In most cases 

 this means the use of water-flushed closets and water-borne 

 sewage. The installation of such necessitates the building 

 of some adequate sewage disposal plant. In some cases, it 

 is necessary simply to pass the sewage into a suitably located 

 concrete cistern or septic tank in which the solid materials 

 settle out and gradually decompose, finally for the most part 

 dissolving in the water. The overflow from this septic tank 

 may be treated in a variety of ways. In some eases 

 it is found practicable to pass it through drainage tile laid 

 in sandy soil, so that the liquid will rapidly seep away into 

 the ground. In other cases filter beds, usually covered and 

 constructed of sand, have been used, with tile laid below. 

 As the effluent from the septic tank spreads out over the 

 sand, it filters through, passes into the tiles below and is 

 carried away to a convenient stream or emptied into some 

 drainage tile. In some cases it is found expedient to install 

 an additional chamber beyond the septic tank which will 

 automatically flush at intervals or when filled to a certain 

 height. Sewage disposal plans show a great variety of 

 types. Directions for their construction and operation may 

 be found in various government and experiment station 

 bulletins. When properly constructed, they probably con- 



