Woodblock illustration from an edition of 1592 (20th year of Wanli reign period of the Ming dynasty), representing the front view of the torso. It shows in diagram form the sequence of transmission and transformation of pathologies through the three Yang channels, from the exterior to the interior, i.e. from the skin, which is governed by the bladder channel of foot taiyang, to the muscles, which are governed by the stomach channel of foot yangming, and thence to the 'semi-superficial, semi-internal' region inside the bodily integument (quqiao) but outside the viscera (zangfu), which is governed by the gall bladder channel of foot shaoyang.