The Yellow Emperor's Classic of Internal Medicine, created in the Warring States period (475 to 221 BC) described a phenomenon whereby the eastern, western, northern, southern, and central regions were liable to different diseases. It brought forward the principle of treatment in accordance with local conditions. Lv's Spring and Autumn Annals, Huai Nan Tzu (Huainanzi), and the Regiment of Health (Yangshenglun) in the Qin, Han, Wei, Jin, and Southern and Northern Dynasties all describe regional diseases such as goiter (endemic goiter) and yellowish teeth (dental fluorosis) as being caused by geologic and climatic factors. Zhang (miasma), first mentioned in the Han Dynasty, was considered related to the summer heat and dampness particular to the geographical environment of the south. Zhang was further associated with malaria in the Jin Dynasty. General Treatise on the Etiology and Symptomology of Diseases (Zhubingyuanhou Lun), in the Sui Dynasty, held that as a type of poisonous gas, Zhang was the predisposing cause of malaria, seasonal disease, and barbiers, among other conditions. General Guide (Zhinan Zonglun), in the Southern Song Dynasty, regarded Zhang malaria as a separate disease. Healthy Prescription in the Southern Wuling District (Lingnan Weisheng Fang), in the late Song and early Yuan Dynasties, explicitly put forward the concepts of cold Zhang, hot Zhang, and lockjaw Zhang. Guidelines for Treatment of Zhang Malaria (Zhangnue Zhinan), in the Ming Dynasty, maintained that cold Zhang was equivalent to malaria, while hot Zhang and lockjaw Zhang were equivalent to cold damage, the latter of which can be treated by prescriptions for cold damage. Records on Zhang gas and Zhang disease decreased during the Ming and Qing Dynasties.