Career
He was an activist of Polish and international workers" movement. He was one of the main activists and creators of the first programme of the Polish Socialist Party. In 1878 Mendelson emigrated to Switzerland, and later lived in France and the United Kingdom.
In 1880 he was accused, together with other activists, in a judicial process with socialists in KrakóWest
Being a skilled organizer and publicist, Mendelson personally befriended many foremost European socialists - Friedrich Engels, Karl Liebknecht, Eduard Bernstein, Karl Kautsky, Paul Lafargue, Georgi Plekhanov and others
