EXPERIMENTAL DAIRY BACTERIOLOGY 



withstand repeated heating to 170 C. without flaking or 

 becoming cloudy, and should be well annealed, so as to 

 withstand sudden changes in temperature. 



For storage of media, and for making the dilutions neces- 

 sary in bacteriological work, flasks are used, usually of the 

 Erlenmeyer form, with narrow necks. The flasks may be of 

 Jena glass, but the many forms of " resistance glass " are well 

 adapted to ordinary purposes, since its 

 solubility is slight. For many purposes, 

 as for dilution work, ordinary bottles 

 may be employed ; they have the ad- 

 vantage of being cheap and economical 

 of space in sterilizers and elsewhere. 



Cleaning glassware. All glassware 

 used in the bacteriological laboratory 

 must be perfectly clean. New glass- 

 ware must be washed in hot water, 

 rinsed in distilled or tap water, and 

 placed for a short time in 1 per cent 

 FIG. 1. TEST TUBES hydrochloric acid, to remove any free 



Board of health pattern, alkali present On the glass. After r ins- 

 one-third size , i T in 



mg, it is drained and allowed to dry. 



Petri dishes, tubes, etc., containing discarded cultures, should 

 not be allowed to become dry, but should be washed as soon 

 as possible. The solid media can be readily removed from 

 test tubes by inserting a piece of glass tubing, which is at- 

 tached to the water tap by a strong piece of rubber tubing. 

 The tube is pushed to the bottom of the test tube and the 

 force of the water ejects the solid matter. Glassware con- 

 taining whole milk, butter, or any fatty substance should not 

 be washed with the ordinary dishes. If the media has been 

 allowed to become dry in the tubes and plates, they must be 



