In 1888 Schulz1 published data indicating that poisonous substances had a stimulatory effect when given in small doses. This became the basis of the Arndt-Schulz law of today. Subsequent work has indicated that this is a general law which extends into areas seemingly far removed from the toxins or chemical substances which first interested Schulz. Thus, not only is the effect noted with chemicals but it may also be observed with such entities as radiation, heat, and cold, and indeed with any agent capable of exerting an effect on cells. The term hormoligosis has been proposed2 to refer to that part of hormology which includes the entire phenomenon of the stimulatory effect of a small amount of an agent on living organisms.
Hormesis3 is that area of hormoligosis which deals with the stimulatory action of a subinhibitory amount of a toxin. Such compounds are known as hormetics.