Hermann Alfred Hirt (1865-1936) taught Greek, Latin and early Germanic languages at Leipzig University from 1892 to 1912 before moving to the chair of Sanskrit and comparative linguistics at Giessen. Born around the time when Bopp and Schleicher were publishing their ground-breaking work on Indo-European, and a young man when Brugmann published his monumental comparative grammar (all available in this series), Hirt began this seven-volume grammar in the 1920s soon after the exciting discovery of Tocharian and the decipherment of Hittite. The project arose out of his extensive research on the historical phonology of Indo-European vowels, which led him to consider much wider issues. Volume 2 (which appeared first, in 1921) revisits and updates Hirt's earlier work on the vowel system, and emphasises the value of comparative philology as opposed to single-language studies. It includes a full index of words.