THE USE OF DOMESTIC METHYLENE BLUE IN 

 STAINING MILK BY THE BREED METHOD 



W. A. WALL AND A. H. ROBERTSON 



iVeto York Agricultural Experiment Station, Geneva, New York 



Received for publication December 15, 1921 



Some difficulty has been experienced in staining preparations 

 of milk by the Breed method. This is well simimarized in the 

 Standard Methods for the Bacteriological Examination of Milk/ 

 as follows: "Some methylene blue now on the market in powder 

 form is very unsatisfactory in that solutions will dissolve the 

 milk films, or will wash them with an even blue color in which 

 the bacteria fail to show distinctly. Old or unfiltered stains are 

 to be avoided as they may contain troublesome precipitates." 



During the past summer an effort was made at this laboratory 

 to find means to correct these difficulties. To this end five 

 samples of methylene blue, all reported to dissolve the milk 

 films, were obtained from H. J. Conn, Chairman of the Committee 

 on Technique of the Society of American Bacteriologists. All 

 proved unsatisfactory when the stain was made up in a saturated 

 aqueous solution using distilled water, and irregular results were 

 obtained upon making up the stain with tap water. It was found 

 that the addition of a small amount (approximately a quarter 

 gram per Uter) of CaCOs in the form of precipitated chalk caused 

 one of the samples to stain without dissolving the films, and the 

 difficulty with another sample was corrected after the CaCOa had 

 stood in the solution for 48 hours. On account of the poor 

 solubility of the CaCOj, NajCOs was tried with uniformly good 

 results. NaHCOa seems to work equally well. This indicates 

 that the addition of small amounts of NaaCOs to aqueous solu- 

 tions of those methylene blues which are worthless because they 



'Third edition, 1921, p. 15, Amer. Pub. Health Assoc, Boston. 



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