A MODIFICATION OF THE TECHNIQUE OF THE VOCES 

 AND PROSKAUER REACTION 



GEO. C. BUNKER, EDWARD J. TUCKER and HOWARD W. GREEN 



Laboratories of Division of Municipal Engineering, The Panama Canal, Canal Zone, 



Panama^ 



Received for publication October 17, 1917 



Summary. The use of Syracuse watch glasses, 1 cc. of glucose 

 potassium phosphate broth— incubated for forty-eight hours at 

 30°C. — and 0.5 cc. of a 45 per cent solution of sodium hydroxide, 

 permits the development of a definite color reaction in this test 

 in a maximum period of one and one-half hours after the addition 

 of the latter solution. 



While engaged in a study of the members of the colon group 

 in the local water supplies a comparison was made between the 

 methods for this test as described in Clemesha's "The Bacteri- 

 ology of Surface Waters in the Tropics" and in the latest edition 

 of ''Standard Methods." Clemesha employed a medium con- 

 sisting of 10 grams of peptone and 5 grams of glucose in 1000 cc. 

 of water with the following procedure: 



The Voges and Proskauer reaction is completed by adding a few 

 drops of a very concentrated solution of caustic potash after forty- 

 eight hours' (or more) incubation. The red colouration nearly always 

 appears within an hour, but in some cases it is delayed. The tubes 

 are, however, kept for twenty-four hours after the caustic potash has 

 been added. 



On a following page of his book he wrote : 



Some care has to be exercised, as in all similar reactions, for in some 

 cases the colour is rather faint. If, however, a very small quantity 

 (2 or 3 drops) of a saturated solution of caustic potash is used, instead 



1 Correspondence should be addressed to senior author, Balboa Heights, 

 Canal Zone. 



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