The desirability of producing a perfect milk is now generally recognized. The production of milk in which there is only an extremely small amount of dirt is, however, an expensive process and one which ordinarily necessitates an increased price. The desire to supply milk of a good quality at a moderate price has resulted in the use of various methods of handling milk. The centrifugal separator has been recognized since its introduction as a means of removing a part of the undesirable elements from milk; however, objections have been raised to the use of these machines and recently centrifugal machines designed especially for the removal of foreign material from milk, known as milk clarifiers, have been put upon the market.

Milk clarifiers, if their increasing use can be taken as an index, are destined to hold an important place in the modern milk plant. The desire to secure additional information regarding the effect of clarification on the bacterial content of milk, the cell content, and the bacterial content where pasteurization is used, as well as to secure data on the bacterial and cell contents of the clarifier slime, has led to the work herein reported.