[...] analogy not only regularizes irregularities [...] but introduces disturbances, generally in favor of greater simplicity or regularity, [...]. These analogical adjustments are practically always symptoms of the general morphological drift of the language.
- Sapir (1921), Pag. 189

Such analogical plurals as 'Baum' 'tree': 'Bäume' (contrast Middle High German 'boum: boume') and derivatives [...] show that vocalic mutation has won through to the status of a productive morphologic process.
- Sapir (1921), Pag. 190

In practice phonetic laws have their exceptions, [...] more apparent than real. They are generally due to the disturbing influence of morphological groupings [...] which inhibit the normal progress of the phonetic drift. It is remarkable with how few exceptions one need operate in linguistic history, aside from 'analogical leveling' (morphological replacement).
- Sapir (1921), Pag. 180

[...] centuries later was the alternation of 'o' and 'e' reinterpreted as a means of distinguishing number; 'o' was generalized for the singular, 'e' for the plural. Only when this reassortment of forms took place was the modern symbolic value of the' foot: feet' alternation clearly established. [...] A type of adjustment generally referred to as 'analogical leveling.'
- Sapir (1921), Pag. 184