Three Maxims for the Study of the Nutrition of Microorganisms

I. The relative potencies of two materials cannot be arrived at by the comparison of the effects of the two materials at equal concentrations. Corollary: The effect of treatment upon the potency of a material cannot be determined by the comparison of the treated and untreated material at equal concentrations. II. The relative potencies of two materials at one temperature may not be true for any other temperature. Corollary: Temperature coefficients for the effect of a material must be determined under optimum conditions for each temperature. III. If two materials are to be compared as a source of a protoplasmic constituent the physical chemical effects of the materials must be compensated for