'Über den Umlaut: Zwei Abhandlungen' (Carlsruhe, 1843) and 'Über den Ablaut' (Carlsruhe, 1844)

Über den Umlaut (1843) and Über den Ablaut (1844) grew out of a review of Grimm’s Deutsche Grammatik by Holtzmann, in which he also made an excursus into Bopp’s theory of vowel gradation in Sanskrit. Holtzmann was the first to observe the correlation of guṇa and accent. At the same time he noted that loss (or absence) of the accent could mean loss or shortening of a vowel. Observations which, be it in a different form, eventually found their way into a unified theory of Indo-European vowel grada