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 Rajchman the first cousin of Ludwik Hirszfeld, a Polish microbiologist. Ludwik Rajchman is the father of Jan A. Rajchman, a Polish computer scientist, inventor of magnetic-core memory. Rajchman grew up in Warsaw in the difficult conditions of the Russian occupation. At an early age, he and his sister Helena became keenly aware of the social injustices in their "country" (Poland did not officially exist at the time) and were involved as teenagers in teaching young workers. As an adult, he joined the Polish socialist party (PPS) and was involved in the 1905 uprising and even arrested. After several months in prison