By Hilary and Peter Butler from their book From One Prick To Another, (2008)
In times long since gone, any pharmaceutical product used to be tested for safety, with one group of people using the drug and another group, the “control” group, using a placebo.
A placebo, in the context of a drug trial, was represented by an “inert” substance; something which had absolutely no impact on any biochemical, immunological or other measurable function in the body. In this way, the studies used to compare any adverse biological “effect” of the drug against the effect of nothing.