Woodblock illustration from Waike xinfa zhenyan zhinan (Guide to Tried and True Methods at the Heart of External Medicine), published in 1887 (13th year of the Guangxu reign period of the Qing dynasty). In Chinese medical theory, there exists a system of correspondences between the three sectors of the pulse -- cun (Inch), guan (Pass) and chi (Foot) -- in the left and right wrists, and the internal organs of the human body. In general terms, these three sectors are often said to correspond to the shangjiao, zhongjiao and xiajiao (Upper, Middle and Lower Burner) respectively. More precisely, according to this text, the left cun pulse corresponds to the baoluo (Heart Envelope) and heart, the left guan pulse corresponds to the gall bladder and liver, and the left chi pulse corresponds to the bladder and small intestine and kidney; the right cun pulse corresponds to the centre of the chest and the lung, the right guan pulse corresponds to the stomach and spleen, and the left chi pulse corresponds to the large intestine and kidney.