Anton Graff (1736-1813), The physician and philosopher Johann Georg Ritter von Zimmermann (1728-1795), 1772-1773. Oil on canvas, 54,00 x 46,00 cm. Ident.Nr. 1034E. Gemäldegalerie, Berlin © Photo: Gemäldegalerie der Staatlichen Museen zu Berlin - Preußischer Kulturbesitz. Photo: Volker-H. 

The sitter, whose identity through a reproductive engraving of Heinrich Pfenninger (1749 - 1815) is occupied, native of Brugg in the canton of Aargau, where he held the post of town physician since 1752nd He maintained close relations with Johann Kaspar Lavater, and was successful as a writer. In 1768 he was promoted to Zimmermann's personal physician of King George III. of Great Britain and Ireland. At the electoral residence Hannover the doctor maintained a lively correspondence with the Russian Empress Catherine II., With Johann Wolfgang von Goethe and Friedrich the Great, whom he treated in Sanssouci Potsdam shortly before his death in August 1786. The 1776 councilor became Johann Georg Ritter von Zimmermann died 1795 in Hannover. 
The painting (Ident. No. 1034E) is the replica of the on behalf of the Leipzig publishing bookseller Philipp Erasmus Reich in September 1771 in Berlin made by Anton Graff painting. The suffering from a serious illness by Zimmermann stayed namely due to a necessary operation in the Prussian royal residence. 
The sitter was later thought that this painting documenting his still poor health.