In medicine Jews were pre-eminent in the Slavonic countries, as they were everywhere else. They were in great demand as court physicians, though several had to pay with their lives "for having failed to effect cures." Doctor Leo, who was at the court of Moscow in 1490, was mentioned above. Jacob Isaac, the "nobleman of Jerusalem" (Yerosalimska shlyakhta), was attached to the court of Sigismund, where he was held in high esteem. Prince Radziwill's physician was Itshe Nisanovich, and among those in attendance on John Sobieski were Jonas Casal and Abraham Troki, the latter the author of several works on medicine and natural philosophy.[34] Medieval Jewish physicians were prone to travel, and those of Russo-Poland were no exception. We find them in almost every part of the civilized world, and their number increases with the disappearance of prejudice. Some were noted Talmudists, such as Solomon Luria and Samuel ben Mattathias. Abraham Ashkenazi Apotheker was not only a compounder of herbs but a healer of souls, for the edification of which he wrote his _Elixir of Life_ (_Sam Hayyim_, Prague, 1590). To the same class belong Moses Katzenellenbogen and his son Hayyim, who was styled Gaon. In 1657 Hayyim visited Italy. He was welcomed by the prominent Jews of Mantua, Modena, Venice, and Verona, but he preferred to continue the practice of his profession in his home town Lublin.[35] Nor may we omit the names of Stephen von Gaden and Moses Coen, because of their high standing among their colleagues and the honors conferred upon them for their statesmanship. Stephen von Gaden, who with Samuel Collins was physician-in-ordinary to Czar Aleksey Mikhailovich, was instrumental in removing many disabilities from the Jews of Moscow and in the interior of Russia. Moses Coen, in consequence of the Cossack uprising, escaped to Moldavia, and was made court physician by the hospodar Vassile Lupu. But for Coen, Lupu would have been dethroned by those who conspired against him. To his loyalty may probably be attributed the kind treatment Moldavian Jews later enjoyed at the hands of the prince. Coen also exposed the secret alliance between Russia and Sweden against Turkey, and his advice was sought by the doge of Venice.[36]