These are terms that were traditionally used in painting and calligraphy theory and literary criticism to refer specifically to a vigorous and forceful manner or style of execution in combination with softer, more feminine touches. In physiognomy, which was popular during the Qin and Han period, gu (骨) referred to the human frame and rou (肉), the skin and flesh. By the Late Han, Wei and the Six Dynasties, the term came to be employed in literary criticism as well. In the field of painting and calligraphy, “bones” were virile and energetic strokes whereas “flesh” was the heavy use of ink or color to create an effect of elegant plumpness. In literary writing, “bones” meant a sturdy overall structure, and “flesh,” any appropriate rhetorical or formal means employed to fill it out. Bones and flesh, when mentioned together, refer metaphorically to the relation between the framework (i.e., the moral message and structural features) and the nuanced aspects of expression of a literary work. They also imply a union between the essential idea and sentiment of a literary work and its formal beauty.

Only if one combines robust and powerful strokes with subtler means of expression will he be able to reach a state of supreme sophistication and to communicate with spiritual beings. (Wang Sengqian: "In Praise of the Dynamic Beauty of Calligraphy")

In writing an essay, content and feeling must be treated as its soul, facts and reasoning as its marrow, and rhetoric and wording as its flesh and skin. Harmony in rhyme must be relied upon to enhance its charm and strength. (LiuXie: The Literary Mind and the Carving of Dragons)