Edward Sapir (18841939). Language: An Introduction to the Study of Speech. 1921.
ingetym-ad to be sleeping and the past ingetymash.
Consonantal change as a functional process is probably far less common than vocalic modifications, but it is not exactly rare. There is an interesting group of cases in English, certain nouns and corresponding verbs differing solely in that the final consonant is voiceless or voiced. Examples are wreath (with th as in think), but to wreathe (with th as in then); house, but to house (with s pronounced like z). That we have a distinct feeling for the interchange as a means of distinguishing the noun from the verb is indicated by the extension of the principle by many Americans to such a noun as rise (e.g., the rise of democracy)pronounced like ricein contrast to the verb to rise (s like z).
In the Celtic languages the initial consonants undergo several types of change according to the grammatical relation that subsists between the word itself and the preceding word. Thus, in modern Irish, a word like bo ox may under the appropriate circumstances, take the forms bho (pronounce wo) or mo (e.g., am bo the ox, as a subject, but tir na mo land of the oxen, as a possessive plural). In the verb the principle has as one of its most striking consequences the aspiration of initial consonants in the past tense. If a verb begins with t, say, it changes the t to th (now pronounced h) in forms of the past; if it begins with g, the consonant changes, in analogous forms, to gh (pronounced like a voiced spirant19g or like y, according to the nature of the following vowel). In modern Irish the principle of consonantal change, which began in the oldest period of the language as a secondary consequence of certain phonetic conditions, has become one