The German linguists Johannes Schmidt (1843-1901) and Hugo Schuchardt (1842-1927) sought to answer many questions relating to the development of Indo-European languages, which are all believed to be descended from a single common ancestor. Schmidt's Verwantschaftsverhaltnisse was originally published in 1872 and Schuchardt's Uber die Lautgesetze followed in 1885; here they are reissued together in one volume. Schmidt's work developed the 'wave model' of language change, to which Schuchardt also subscribed. According to this theory, linguistic innovations spread outwards concentrically like...