He then did further postgraduate studies in Europe, first in Prof. Friedrich von Müller's Clinic at the University of Munich in Germany (1914) then, after the mobilisation of the German army, in the Polyclinic Umberto I at the University of Rome in Italy (1915). After the earthquake in the Abruzzi mountains in January 1915, Hume was put in charge of the medical relief expedition organized by the U.S Ambassador to Italy. He stayed in the country until recalled to America by his mother's death in 1916.