The examination for mold is made with the ×6 ocular and 16 mm objective, giving a magnification of approximately 90 times. About 50 fields are supposed to be examined and the result expressed in terms of the per cent in which mold was found. It is stated that it is believed that manufacturers can conduct their operations so that mold will not be present in more than 25 per cent of the fields. There are, therefore, three units in which to express the results: bacteria in cubic centimeters, yeasts and spores in one-sixtieth of a cubic millimeter, and molds in percentage of microscopic fields. Aside from the errors which may occur in the manipulation of the purely mechanical part of the technique, there are other considerations which affect the accuracy of the results. First, the differentiation between organisms and tissues is not considered possible by most pathologists and bacteriologists without differential staining. Even in such simple examinations as those for diphtheria and tuberculosis, a stain is required. In foods the particles of the plant tissue and the organisms are not so different that they can be clearly separated without using similar technique. It is possible to make some separation, but not with accuracy. Threads of protoplasm may be mistaken for bacilli; the granular contents of a cell for cocci, yeasts, or spores; bits of cell wall for hyphae under the magnifications given, and the results obtained be high or low, depending upon the personal ability of the operator. Each error magnified by the enormous factor used in calculating the final result naturally gives figures which may be far above or below the truth. Those who have had special training in plant structure and bacteriology are likely to give the higher figures, while those who have had these subjects as incidentals in a scientific course are apt to give much lower ones.