The German compound word Wirkstoffe, combining agency (wirken) with materiality (Stoff), is hard to translate. The English term ‘biologically active substances’ as well as the Dutch actieve substantie, the Spanish sustancia activa, or the French substance active fail to capture its full meaning. While it had not been widely used before the first decade of the twentieth century and then mostly in the sense of a specific fabric or as synonymous with an initial power, it gained prominence in the 1930s as a biochemical concept uniting a new physiology of effective substances and the industrial production of pharmaceuticals with a life-reform discourse on a pure and strengthened body. Well into the 1950s, the term Wirkstoffe exclusively referred to enzymes, hormones and vitamins as chemical agents that, although minute in quantity, showed profound physiological and biological effects. These biologically active chemical substances were vital to the organism due to their capacity to regulate the metabolism and the functioning of tissues and cells; but as standardized biologics, defined by their ability to compensate for deficiencies, they were also pharmacological actors, agents that promoted healthy and efficient bodies.

Research on and development of these strictly speaking hypothetical substances, at least in the first third of the twentieth century, was far from a German speciality. Indeed, interest in them extended to all transatlantic countries, notably the US, Canada, Great Britain, France, Switzerland, Spain and the Netherlands.