H. Smidt in a recent note on the reduction of methylene blue by means of milk confirmed the results of Schardinger that a mixture of formaldehyde and methylene blue is decolorised by the action of milk. This reaction depends on the presence of a ferment—a catalase—in the milk, and, as this ferment is readily destroyed by heat, serves as a very simple method of determining whether a given sample of milk is “raw” or not. By way of conclusion Smidt stated that he thought this test might be of still further utility in that it might be possible to estimate the degree of bacterial contamination of the milk by its means. If such a comparatively simple test could be employed, in an easy and effective fashion, it would be of immense service, as, owing to the rapidity with which it can be carried out, the milk could be examined before distribution.