How were the efficacy or pharmacology of Chinese medicines determined?

The efficacy and effectiveness of herbal medicine was a discovery made by the ancients through practice. Through labor it was discovered by chance that a certain herb had this effect. The second is through imitating other animals to cure diseases, for example, when a rabbit was bitten by a snake it would seek out the white-flowered snake's tongue herb to eat and be cured, and when a monkey broke a bone it would seek out the bone-breaking tonic to cure it, and so on and so forth, to name but a few examples. In this case, the experience was accumulated through human observation of animals and their own experiments. In this way, from nothing to something from something to more accumulated and passed on from generation to generation.