Lewisohn was born to German-Jewish[2] parents in Hamburg and was educated at the local Gymnasium from where he entered medical school in Kiel in 1893.
[1] Working independently, Lewisohn's contribution, in 1915, was to determine the optimal concentration of sodium citrate for preserving blood products without inducing toxicity (0.2% for transfusions not exceeding 5g).
[5] He had traveled previously to Hans von Haberer in Innsbruck, Austria, where the method had already been applied and where he became familiar with the surgical techniques.
[5] Following the successful application at Mount Sinai, the technique spread to the rest of the United States for ulcers resistant to other treatment.
[3] Lewisohn was also a contemporary of Alexis Moschcowitz and his successor as chief of the general surgical service at Mount Sinai.