Determination of logarithmic averages of bacterial counts is a necessary and laborious task in grading raw and pasteurized milk. As the plate count determination replaces the methylene blue test for the ever increasing number of bulk milk producers, the problem becomes greater. A slide rule type of device has been developed that may materially simplify this task. This method is explained with information relative to its principle, application, accuracy, and advantages.

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Author notes

John C. Schilling received the B. S . Ch. E. degree from the Missouri School of Mines in 1943. He served in World War II after graduation, and was employed by the St. Louis Health Division as a Public Health Engineer in 1946. After varied experience in sanitation, industrial hygiene and rodent control work, he was assigned to his present position of Dairy Plant Engineer in the Milk Control Section. He has held this position since 1951.