The evidence for alternation presented by Edgerton was of two sorts. He cited several hundred passages from the Rigveda, which he claimed should be rescanned to reveal hitherto unnoticed expressions of the syllable structure called for by his theory. But most forms show no such direct expressions; for them, Edgerton noted sharply skewed distributions that he interpreted as evidence for a lost alternation between syllabic and nonsyllabic consonants (commonly called "semivowels" in the literature). Thus say "śiras" "head" (from ) has no monosyllabic partner **"śras" (from ), but Edgerton noted that "śiras" occurred 100% of the time in the environments where his theory called for the syllabification of the . Appealing to the "formulaic" nature of oral poetry, especially in tricky and demanding literary forms like sacred Vedic versification, he reasoned that this was direct evidence for the previous existence of an alternant , on the assumption that when (for whatever reason) this *"śras" and other forms like it came to be shunned, the typical collocations in which they would have (correctly) occurred inevitably became obsolete pari passu with the loss of the form itself. And he was able to present a sizeable body of evidence in the form of these skewed distributions in both the 1934 and 1943 articles.