Thomas and Breinl discovered that arsanilic acid, was more potent in the treatment of laboratory trypanosomiasis than arsenic in inorganic form. As a crystalline powder it was introduced medically as Atoxyl. Thomas and Breinl recommended high doses, given continously for human typanosomiasis. The above is Memoir XVI of the Liverpool School of Tropical Medicine. The drug was soon found to be prohbitively toxic for human use and taken off the market.