The German linguist Hugo Schuchardt (1842–1927) made significant contributions to the study of the Basque and Romance languages, publishing also on pidgins and creoles. A critic of the Neogrammarian hypothesis of sound laws, he subscribed to the 'wave model' of language change. His Über die Lautgesetze: Gegen die Junggrammatiker (1885) has been reissued in this series in a volume with Die Verwantschaftsverhältnisse der indogermanischen Sprachen (1872) by Johannes Schmidt (1843–1901). Based on Schuchardt's doctoral dissertation and the painstaking study of extant sources, the present three-volume work appeared between 1866 and 1868. He explores here the development and characteristics of Vulgar Latin, the language of the general population, as opposed to the classical, literary variety. The work focuses on the distinctive vowel changes that took place in Romance vernaculars over many centuries. Volume 1 (1866) examines qualitative vowel changes. Volume 2 (1867) includes discussion of quantitative changes. Volume 3 (1868) is a supplement and includes corrections.