Woodblock illustration from Shejian bianzheng (Pattern Differentiation in Tongue Examination), a Chinese manual of tongue diagnosis, published in 1905 (31st year of the Guangxu reign period of the Qing dynasty) -- simple line drawing, showing the features of the tongue morphology known as hongzhong danhei she (red tongue with pale black centre). The body of the tongue is reddish with a pale black coating on the central part. This is a sign of excess-heat in the internal organs. If heat from cold damage penetrates into the interior, this results in thoracic accumulation with distress and restlessness (jiexiong fanzao), constipation and urinary retention and glazed, staring eyes; and epidemic toxins (yidu) may directly attack the three Yin channels. In all such cases, this tongue morphology is seen. It is treated with Shiquan kuhan jiubu tang (Peerless bitter-cold rescue and tonic decoction) - composed of gypsum, zhimu (rhizome anemarrhenae), huangqin (radix scutellariae), huanglian (rhizome coptidis), huangbai (cortex phellodendri), dahuang (rhubarb), mangxiao (sodium sulfate), houpo (cortex magnoliae officinalis), zhishi (fructus aurantii immaturus) and rhinoceros horn.
