124 A MANUAL OF BACTERIOLOGY 



place in the filtering cylinder. The solution to be filtered is poured 

 into the large end of the cylinder, which is connected with the air 

 tank. A piece of glass tubing with a rubber-tubing connection is 

 slipped on the nipple end of the bougie. This tubing should pre- 

 viously be sterilized in 1 : 1000 bichloride solution or in 70 per cent 

 alcohol, and rinsed with sterile distilled water. 



A cotton-plugged Erlenmeyer flask which was previously dry 

 sterilized is placed to receive the filtrate. The cotton forms a pack- 

 ing around the glass tubing. The time of filtration varies with the 

 pressure and the nature of the solution to be filtered. With a pres- 

 sure of 1 atmosphere the filtration will usually be rapid. 



The bougie can easily be removed fcr cleaning by unscrewing the 

 cap at the bottom of the cylinder. The scum on the exterior can be 

 removed by washing in water, using a small brush with stiff bristles. 

 Care should be taken to prevent wash water from entering the mouth 

 of the bougie. After washing, rinse in distilled water and dry it for 

 resterilization. A Chamberland bougie may be used continuously for 

 two or three days before resterilization is necessary. Continued use 

 should be avoided, since colonies of microorganisms may grow 

 through the wall of the filter bougie. 



When the bougie has been used for some time, its efficiency is 

 impaired and the filtration goes very slowly. The difficulty is due 

 to the clogging of the pores of the filter with organic matter. The 

 bougie should be dried and heated to redness above a Bunsen flame 

 for half an hour. This can be done by hanging the bougie with the 

 nipple upward in a cylinder of sheet iron covered with asbestos 

 and partially covered at the top and bottom with asbestos rings. A 

 single Bunsen burner placed at the bottom will heat the tube to 

 redness in a short time. 



After cooling, place the bougie in the filtering cylinder and run 

 distilled water through it, to wash out the charred organic matter. 

 This treatment of the bougies restores them to their former efficiency. 



STERILIZATION BY MEANS OF LIGHT 



It is almost universally admitted that sunlight is one of the best 

 and cheapest of germicides, but for rapid work light is not eco- 

 nomical. Recent work by Henri and his associates shows that the 

 ultra-violet light of a quartz-tube mercury lamp may give complete 

 sterilization of water and sewage without producing any chemical 



