Quantification of toxic response and the development of the median effective dose (ED50)--a historical perspective

The development of the widely-used median effective (or lethal) dose as a summary measure in quantifying toxic response to chemical stimuli is reviewed. Attention is directed at those mathematical properties noted by the originator of the median effective dose, the English physiologist John William Trevan, that make the measure a useful summary statistic for toxicological studies. Consideration is also given to the development of precursor measures to the median effective dose, such as minimal effective dose.