Atropa belladonna
His prolific output, mainly in chemical pathology, included research into the metabolism of glycogen, uric acid, and urea; studies into an epidemic of cholera in Amsterdam; the toxicity of "Atropa belladonna" (deadly nightshade); various pigmented substances in the blood (including porphyrins); the nature of the heart sounds; and several contributions in tropical medicine, in which he was considered an expert. He also described the blood disorder methaemoglobinaemia.