AN INQUIRY INTO THE USEFULNESS OF THE STANDARD METHODS DIRECT MICROSCOPIC COUNT1

Abstract

Microscopic technics are not capable of yielding “accurate numerical estimates” of the bacteria in “market grade” row milks, because of (a) the small number of cells available, and their random distribution; (b) the pattern of solids deposition and (c) the “working factors” dictated by the smear areas examined. While multiple strip viewing reduces working factors, the order of accuracy attainable is far short of that yielded by the agar plate method, and the effort which must be expended is much greater.