252 



APPLIED PHYSIOLOGY 



449. Danger from sewage. Sewage often is a poison 

 itself, and when much is collected it often develops poisons 

 by its decay. The foul smell of sewage is due to gas 



called sewer gas. While 

 the gas itself is but slightly 

 harmful, yet it is a sign 

 of decay and of lurking 

 sources of danger. But 

 sewage is dangerous mainly 

 because it may contain 

 germs of typhoid fever 

 and other diseases which 

 come from the excretions 

 of sick persons. 



450. Disposal of sewage. 

 In thinly settled country 

 places small quantities of 

 slops and sewage may 

 safely be emptied in the 

 back yard, for the soil de- 

 stroys and removes all of- 

 fensive matters and disease 

 germs, so that only pure 



water from being sucked out of the 



tra p. water reaches the deeper 



d waste pipe, down which the slops pass ] a y ers o f the ground. If 



into the sewer. 



e pipe from the gutter on the roof. a house has a bath TOOm, 



/ waste pipe passing under the street. there win be SQ much waste 



g ventilation pipe. 



water that some device will 



be needed for its disposal. The simplest contrivance is to 

 conduct the sewage into a hole called a cesspool, from 

 which it slowly soaks into the ground. A cesspool should 

 always be so located that the underground flow of water 

 from it will be away from any wells (p. 1 36). 



Diagram of the plumbing of a house. 

 a sink or washstand. 



b trap, which remains full of water and pre- 

 vents the entrance of sewer gas. 

 C air pipe for ventilation and to prevent the germs 



