He had been dividing his time between the faculties of Wellesley, Middlebury, and Johns Hopkins but in 1940 he took up a permanent post at Johns Hopkins where he remained for the rest of his life, including long spells of travel in South America and a period of 3 years at the University of Puerto Rico. In the summer of 1949 he returned to Europe for the last time to visit Italy and France and to work for UNESCO. At the beginning of 1951 he began to exhibit signs of ill-health, which turned out to be an incurable cancer. He died on 4 December 1951. At his request he was buried in Santa Maria Magdalena de Pazzis Cemetery in San Juan.