Credit: Wellcome Library, London. Wellcome Images images@wellcome.ac.uk http://wellcomeimages.org Woodblock illustration from an edition of 1738 (3rd year of the Qianlong reign period of the Qing dynasty). It shows the tongue morphologies known as 'black tongue with prickly underside' (cidi heishe) and 'tongue black and rotten from being bitten' (heilan zi nie she).With patients presenting with black tongue with prickly underside, if the surface of the tongue is prickly when the coating is scraped off, and the body of the tongue is mostly black, the condition is generally incurable. If, however, the body of the tongue is reddish, there is hope that the patient will survive if the internal heat is cleared. With 'tongue black and rotten from being bitten', if the tongue appears black and rotten and the patient has a constant urge to bite it, generally in conjunction with dehydration and burning heat, there is no possible remedy. Once the blackness and rottenness has spread to the root of the tongue, death is inevitable. Woodcut Library of Zhongguo zhongyi yanjiu yuan (China Academy of Traditional Chinese Medicine) Shang Han Yi Yan (Medical Experience Concerning Cold Damage) Lu Yuncheng (Qing period, 1644-1911) Published: 1738