28 



METHODS OF STERILISATION 



NOTE. Tubes, flasks, filter flasks, pipettes, glass tubing, etc., 

 may be rapidly sterilised, in case of emergency, by washing, in 

 turn, with distilled water, perchloride of mercury solution, alco- 

 hol, and ether, draining, and finally gently heating over a gas 

 flame to completely drive off the ether vapor. Chloroform or 

 other volatile disinfectants may be added to various fluids in 

 order to effect the destruction of contained bacteria, and when 

 this has been done, may be completely driven off from the fluid 

 by the application of gentle heat. 



Dry Heat. The naked flame of the Bunsen burner 

 is invariably used for sterilising the platinum needles 

 (which are heated to redness) and may be employed 

 for sterilising the points of forceps, or other small 



instruments, cover-glasses, pi- 

 pettes, etc., a very short ex- 

 posure to this heat being 

 sufficient. 



Ether Flame. In an emer- 

 gency small instruments, 

 needles, etc., may be sterilised 

 by dipping them in ether and 

 after removal lighting the 

 adherent fluid and allowing 

 it to burn off the surface of 

 the instruments. Repeat the 



FIG. 25. Muffle furnace. 



process twice. It may then be safely assumed that the 

 apparatus so treated is sterile. 



Muffle Furnace (Fig. 25). Although this form of 

 heat is chiefly used for the destruction of the dead 

 bodies of small infected animals, morbid tissues, etc., 

 it is also employed for the sterilisation of porcelain 

 filter candles (vide p. 42). 



Filter candles are disinfected immediately after use 

 by boiling in a beaker of water for some fifteen or 

 twenty minutes. This treatment, however, leaves the 

 dead bodies of the bacteria upon the surface and block- 

 ing the interstices of the filter. 



To destroy the organic matter and prepare the filter 

 candle for further use proceed as follows : 



