Kammala jumlar da ke gaba: An haifi Lorentowicz a Pabianice, a cikin tsakiyar Poland na yau, a cikin 1868, shekaru biyar bayan buɗewar
Tashin hankalin Poland na 1863 wanda sojojin Rasha suka murkushe shi. Iyayensa sun yi ƙaura zuwa tsakiyar Poland ta yau daga tsohuwar iyakar "Kresy" ta gabas, suna tserewa talauci da zalunci. Jan ya sami takardar shaidar makarantar sakandare a Płock ta hanyar karatun gida kuma ba da daɗewa ba ya tafi Faransa, inda ya zauna har zuwa 1903 kuma ya yi karatu a Sorbonne.