It has been found that the reductase test gives a considerably higher estimate of the number of organisms present in some milk samples than the plate method. This, however, is doubtless due to the fact that many colonies obtained by plating do not arise from a single cell but from chains of cocci and bacilli. Again the plate method takes no account of the anaerobic bacteria present in the milk.

When there are more than 100,000 organisms per cubic centimetre in the milk it would seem that the reductase test gives just as accurate an estimate as the plate method.

In its present form, however, the test would not be of service in grading of milk according to the bacterial standards now suggested.