Interlinguistics of interlinguistics are, however, not so constructive, but rather descriptive, comparative, historic, sociolinguistic, or concerned with translation by humans or machines. As for Esperanto, which is the most widely used constructed interlanguage, there is a relatively abundant literature about the language itself and its philology (see Esperantology). Only a few of the many constructed languages have been applied practically to any noteworthy extent. The most prosperous were Volapük (1879, Johann Martin Schleyer), Esperanto (1887 Ludwik Lejzer Zamenhof), Latino sine flexione (1903, Giuseppe Peano), Ido (1907, Louis Couturat), Occidental-Interlingue (1922, Edgar de Wahl) and Interlingua (1951, IALA and Alexander Gode), with
Ludwik Krzywicki in the organization and management of scientific bodies. He served as vice-director of the Central Statistical Office, taught at the University of Warsaw (1919–36) and other institutions of higher education, and directed the Socio-Economic Institute. During World War II he was injured during the defence of Warsaw in September 1939, and the bomb that destroyed his apartment also caused the loss of most of his papers and manuscripts. His working conditions worsened and he died of heart disease in 1941. Ludwik Krzywicki Ludwik Krzywicki (21 August 1859 – 10 June 1941) was a Polish anthropologist, economist and sociologist. One of