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BACTERIOLOGY 



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60 a 

 S5 



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been used by the Committee^ on 

 the Descriptive Chart of the Society 

 of American Bacteriologists. To the 

 left oi P„ =7 is the acid range and 

 to the right of 7 the alkaline range. 

 The useful range of each indicator is 

 shown by the heavily shaded portion 

 of the respective curve. 



Gelatin. — Finely chopped meat, 

 f & 450 to 500 grams, is mixed with a 

 liter of distilled water and digested 

 on the water bath for half an hour 

 at 50-55°, with stirring. It is then 

 strained through muslin, yielding a 

 filtrate of deep red color, which 

 should be made to equal 1000 c.c. 

 This filtrate is placed in the inner 

 compartment of a double boiler (rice 

 cooker) and to it are added 10 grams 

 peptone, 5 grams sodium chloride 

 and 100 to 150 grams of sheet gelatin 

 of the best quality ("gold label" 

 gelatin). The larger amount of 

 gelatin should be used during warm 

 weather if no low temperature in- 

 cubator is at hand. These con- 

 stituents are dissolved by stirring at 

 a temperature below 55° C. After 

 complete solution, the reaction is 

 titrated as has been described for the 

 titration of broth. From 30 to 50 

 c.c. of normal alkali are usually re- 

 quired to give the proper reaction 



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' Conn, H. 

 1919, IV, 107. 



J. and others: Journ. Bact., 



