That's skipping a few steps. When insulin was discovered in 1921-2, it was only known that a pancreatic extract that has gone through some specific chemical pr

That's skipping a few steps. When insulin was discovered in 1921-2, it was only known that a pancreatic extract that has gone through some specific chemical processes could lower blood sugar. International units of insulin were initially defined not by the quantity of material, but rather by their effect. An international unit was defined to be the amount of extract that once given to a 24-hour fasted 1 kg rabbit, would lower its blood glucose level to 45 mg/L. Only in the 1950s, it was discovered that insulin was a specific protein, and the definition was updated accordingly. We could use rhino horns well before the chemical is isolated and a synthesized.