General Principles of Biological Assays

This chapter discusses the general principles of biological assays. In designing a satisfactory assay, the first stage is to determine the relation between dosage and response with a single preparation. In each case, the dose that reaches the site of action in the test organism is assumed to be proportional to that measured by the experimenter. As the dose of an active preparation is increased from which it gives no effect to one giving a maximum effect, the response increases (or decreases) continuously to form in many cases a sigmoid curve. An initial objective is to select units of response and of dose that will lead to a straight line over a range that is wide enough for assay purposes. The units used in the calculation are sometimes referred to as metameters. The response metameter varies considerably from one assay to another, but only two dose metameters lead to satisfactory assays. The more important of these is the logarithm of the dose.