ABSTRACT
The reasoning leading to equation (1) illustrates that what is added is dose b and the B-equivalent of dose a such that the sum is the dose B which yields effect E. This criterion, dose equivalence, is the basis used by Loewe for predicting how much of each is needed to achieve the effect level E. When equation (1) is viewed graphically it is seen to be a straight line (Fig. 2) in the first quadrant having intercepts A and B and the points on this line represent all combination dose pairs (a,b) that are expected to yield effect level E. The line segment is called the additive isobole for the
