Iwan Bloch (April 8, 1872 – November 21, 1922), also known as Ivan Bloch, was a German dermatologist, and psychiatrist, psychoanalyst born in Delmenhorst, Grand Ducal Oldenburg, Germany, and often called the first sexologist. Together with Magnus Hirschfeld and Albert Eulenburg, Bloch is known for having proposed the new concept of a science of sexuality (Sexualwissenschaft) or sexology. In 1906 he wrote in German the book Das Sexualleben unserer Zeit in seinen Beziehungen zur modernen Kultur which was translated as The Sexual Life of our Time in its Relations to Modern Civilization, a complete encyclopedia of the sexual sciences in their relation to modern civilization. He is also known for having discovered the Marquis de Sade's manuscript of The 120 Days of Sodom, which had been believed to be lost, and published it under the pseudonym Eugène Dühren in 1904. He had previously published Marquis de Sade: his life and works. in 1899 under the same pseudonym, which he used later for the publishing of more works about Sade and Rétif de la Bretonne. Legacy According to Sigmund Freud, Bloch's studies were instrumental in the development of the anthropological approach to the theory of sexuality. Before Bloch, homosexuality was analyzed using a pathological approach. Handbook of Sexology and other works Iwan Bloch began the publication of his Handbuch der gesamten Sexualwissenschaft in Einzeldarstellungen (Handbook of Sexology in its Entirety Presented in Separate Studies) in 1912. Three volumes appeared until the project was aborted because of Bloch's untimely death at age 50, in 1922. Handbuch der Gesamten Sexualwissenschaft in Einzeldarstellungen (Band 1, Band 2, Band 3: Louis Marcus, Berlin, 1912–25): I. Die Prostitution. Hälfte 1 (1912) II. Die Prostitution. Hälfte 2 with Georg Loewenstein was issued in Berlin by Louis Marcus in 1925 III. Die Homosexualität des Mannes und des Weibes. (with Magnus Hirschfeld) (1914) He had published earlier: Irrungen menschlicher Liebe (n.d., as Veriphantor) Das Versehen der Frauen in Vergangenheit und Gegenwart und die Anschauungen der Aerzte, Naturforscher und Philosophen darüber (1899, as Gerhard von Welsenburg) Der Marquis de Sade und seine Zeit. Ein Beitrag zur Cultur- und Sittengeschichte des 18. Jahrhunderts. Mit besonderer Beziehung auf die Lehre von der Psychopathia Sexualis (1900 as Eugen Dühren 1. Aufl. Barsdorf, Berlin, 1900; Max von Harrwitz, Berlin, 1904; 5. Aufl. Barsdorf, Berlin, 1915, in series:Studien zur Geschichte des menschlichen Geschlechtslebens Bd. 1.; Altogether 7 editions in his lifetime. Reissued in 1978: Heyne,