A cooperative study, involving 12 federal, state, local, and private laboratories throughout the country, was conducted to evaluate six methods of preparing and using the methylene blue stain for the direct microscopic count of bacteria in milk. Three of the six methods were found superior, yielding significantly higher bacteria counts, at the same time providing greater ease in counting. These three methods are: Levine and Black's acid-and-water-free stain; North's aniline oil stain; and Anderson's polychrome stain.

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Author notes

*Submitted Oct. 20, 1953.

Nathan Mantel graduated from the City College of New York in 1939. He has since been taking graduate work in advanced statistics at American University while employed in Washington. He is now in the Biometry Section of the National Cancer Institute, and has been with the Public Health Service since 1947. He has been principally concerned, at the Public Health Service, with the application of statistical methods to biological and medical research.