Maurice Bloomfield was a professor at John's Hopkins University and a great authority on Sanskrit literature and comparative linguistics. In this paper he applies the principles of linguistics to find the proper root forms for Ancient Greek words, a task complicated by the vowel shift that occurs when Greek words (particularly verbs) are inflected. This change of vowel within the word root during the process of declension and conjugation is called ablaut. Bloomfield here devises a consistent rule for finding the proper vowel used in Greek roots. The piece is of some technical complexity, but is clearly written and illustrates the difficulties involved in tracing consistency between Indo-European languages and is of interest to linguists and also to students of Greek wishing to gain a deeper understanding of the mechanics of the language.