266 " Specific " Bacteria in Ventilating Pipes, etc. 



These results show that bacteria existing in sewage under natural condi- 

 tions can be ejected into the air in the same manner as the naked bacteria 

 used in the experiments already recorded. 



Conclusions. 



The experiments show that : — 



(1) Specific bacteria present in sewage may be ejected into the air of 

 ventilation pipes, inspection chambers, drains, and sewers by {a) the bursting 

 of bubbles at the surface of the sewage, (b) the separation of dried particles 

 from the walls of pipes, chambers, and sewers, and probably by (c) the 

 ejection of minute droplets from flowing sewage. 



(2) A disconnecting trap undoubtedly prevents the passage of bacteria, 

 present in the air of a sewer, into the house drainage system. 



(3) An air inlet, even when provided with a mica valve, may be a source 

 of danger when it is placed at or about the ground leveL 



