THE BACTERIOLOGICAL LABORATORY 35 



To use cotton-wool, flasks, and tubes disinfected 

 by prolonged steeping in alcohol, carbolic acid solu- 

 tion, and other chemicals, is not absolutely reliable ; 

 and many failures have been the results of such 

 methods of sterilisation. Therefore, 'it cannot be 

 too thoroughly insisted on that the flasks and test- 

 tubes, and especially the cotton- wool used as plugs 

 for the vessels, 

 should be thor- 

 oughly sterilised 

 by over-heating, 

 for cultivations 

 are as often con- 

 taminated by 

 this not being 

 properly carried 

 out as by the 

 non-sterility of 

 the nourishing 

 fluids or the acci- 

 dental entrance 

 of organisms 

 from the air.' 



For the sterilis- 

 ation of scalpels, 

 forceps,platiuum 



needles, etc., the Bunsen flame is the best way of 

 cleansing them ; but, unfortunately, the naked flame 

 is most destructive to the blades of scalpels; to 

 obviate this, Israel's case was devised. It is a sheet- 

 iron box (with lid), in which the scalpels, etc., are 

 exposed to a temperature of 150C. in the hot-air 



FIG. 12. SERUM STERILISER. 



