Similar Joint Action of Insecticides

Abstract

BLISS¹ defined the similar joint action of poisons in such a way that the quantal responses to mixtures of poisons acting similarly could be predicted from the separate toxicities of the components of the mixtures. Finney² revised Bliss's treatment of the subject, and both Finney² and Swisher³ have shown that mixtures of certain insecticides were of the toxicity so predicted. If z₁ and z₂ are the doses of poisons A and B respectively, the probit responses, y, produced by A and B alone are usually given respectively by: Provided, and only provided, that β₁ = β₂ = β, the probit response to z₁ of A and z₂ of B applied together is, according to Bliss's scheme, predicted by Finney's equation (8.4), which may be conveniently expressed in the form: where h is the base of the logarithms. Equation (3) reduces to (1) or (2) as z₂ or z₁ is made zero. Bliss's hypothesis of similar action does not permit A and B to act similarly if β ≠ β₂.