PART I 



GENERAL MORPHOLOGICAL AND CULTURAL 

 METHODS 



EXERCISE 1. CLEANING GLASSWARE 



Glassware for use in microbiological laboratory work 

 should be not merely clean, but chemically clean. Test 

 tubes, Petri dishes, flasks, etc., are the receptacles used in 

 the microbiological laboratory for containing the different 

 nutrient substances upon which microorganisms are to 

 subsist. Very frequently free alkali may be present on 

 new glassware in sufficient quantity to prevent microbial 

 growths in the nutrients contained therein. Prescott and 

 Winslow in testing out different glassware say that, " The 

 more soluble glassware yielded sufficient alkali to the me- 

 dium to inhibit four-fifths of the bacteria present in certain 

 cases." 



Glassware which looks clean may have been used previ- 

 ously and should be given a thorough cleaning to rid it of 

 possible traces of mercuric chloride, or other chemical having 

 germicidal properties. 



Follow directions carefully and clean all new and appar- 

 ently clean glassware in the order given. 



Cleaning New or Apparently Clean Glassware. All new 

 glassware should first be treated with chromic acid cleaning 

 solution (see appendix for all formula) before proceeding 

 with the directions for cleaning glassware. 



Return used cleaning solution to the glass receptacle 

 provided for the purpose. Do not throw it away. This 



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