本文擬就介音-j-自上古以來對各系聲母的影響來檢查顎化（本文借以兼指軟化、喻化）條例的濫觴與擴散，同時論證中古濁擦音來自上古濁塞（擦）音。顎化是一再重複出現的老例。影響遍及各類聲母，也因而產生了許多新音。如此單項音變規則專史的研究，因為與通史互為表裏，所以既可以整理一連串似不相關而實同類的音變，也可藉以檢查音變的上古源頭的音系、說明一些音韻史上的舊問題，發現前此忽略的新問題，更可提供一個思考的歷史間架，於斷代的研究或有助益；於個別音變的了解，例如輕重唇的分化條件、牙音何時顎化等，也能收大處著眼之效。

This is a brief account of the history of yodization in Chinese from the Archaic period to Modern. Because this sound change stretches for such a long time and has affected almost every single initial consonant, this paper has a good chance to examine how the rule manifasting itself in different types of changes under different conditions and how the rule has diffused structurally and chronologically. It is hoped that an overall view of the history obtained through this study could shed some lights on some blind spots of the previous studies adopting a more fixed focus. Another purpose of this paper is to see, in the light of the general and dominating rule of sound change, whether or not the reconstruction of voiced fricatives, especially that of the velar voiced fricative, is necessary for Archaic Chinese. The voiced fricatives are found noly before the medial -j- in and after Ancient Chinese and the words with such initials are relatively small in number. Besides, the distributions of these initials are either inconsistat among the historical records or often in complementary distribution with their voiced stop or affricate counterparts. This paper demonstrates that the voiced fricatives of Ancient Chinese are derived from their voiced stop or affricate counterparts through yodization. Also discussed are the labiodentalization of bilabials and the palatalization of velars. The former is achieved through the combination of yodization of initial bilabials and their regressive assimilation to the syllabic nuclei in backness; and the latter is achieved from the palatalization of velars accompanied by that of dental sibilants. This paper maintains that, due to the palatalization of dental sibilants in a much later stage, the resulted palatal sibilants, which are otherwise but the allophones of velars, finally acquire the phonemic status. In Modern Mandarin the syllables with the zero initial followed by [i] or [y] are crowded with homohpones. This is explained by the yodization of many voiced initials through the history.