Although Sydenham was a successful practitioner and witnessed, besides foreign reprints, more than one new edition of his various treatises called for in his lifetime, his fame as the father of English medicine, or the English Hippocrates, was posthumous. For a long time he was held in vague esteem for the success of his cooling (or rather expectant) treatment of smallpox, for his laudanum (the first form of a tincture of opium), and for his advocacy of the use of "Peruvian bark" in quartan agues, in modern terms, the use of quinine-containing cinchona bark for treatment of malaria caused by "Plasmodium malariae". There were, however, those among his contemporaries who understood something of Sydenham's importance in larger matters than details of treatment and pharmacy, among them Richard Morton and Thomas Browne who owned copies of several of Sydenham's books.