What is the miasma that Zhuge Liang encountered? Why is there so much miasma in the south and so little in the north?

The so-called miasma is generally considered to be a toxic gas produced by the decay of animals and plants in virgin forests, which cannot be deposited, and people will get sick or die if inhaled.

In fact, this is a general term for the environmental fear of intellectuals centered on the north at that time to underdeveloped areas such as Jiangnan and Lingnan at that time.

The miasma in ancient people, on the one hand, includes the above-mentioned poisonous gas, on the other hand, it also includes a large number of mosquitoes that breed in dense areas of water networks, parasites (such as schistosomiasis) that grow in water networks, and even infectious diseases such as malaria and dysentery.

Because the ancients did not have modern medical knowledge, they could not effectively distinguish the above different situations, that is, they took the southern wilderness as a general term.

For the people of China at that time, the ecological difference between the north and the south of the great river was no less than that of people watching Mars on the earth today.

In the eyes of the ancients, miasma belongs to a kind of epidemic febrile disease. On the Cause of Disease and Climate: "The green and yellow awn in the south of Fuling Mountain is like typhoid fever in the north of Lingling Mountain. It's warm in the south, so when it's too cloudy, flowers and trees don't turn yellow, and they crouch and don't hide, because it's warm and poisonous. Therefore, Lingnan swims from mid-spring to mid-summer, and travels from Mengdong to Huangmang in late summer. "

Here we have arrived in Lingnan. At the end of the Eastern Han Dynasty, Zhang Zhongjing's Treatise on Febrile Diseases contained many prescriptions for treating fever. He was from Nanyang and moved to Changsha County, which is today's Hunan. It can be seen that Hunan was still a "land of boils".

By the Tang Dynasty, Hunan was already an inner county, and Lingnan, Yongguan and Qianzhong were imaginary areas of miasma.

By the Ming and Qing Dynasties, miasma had become the exclusive of the mysterious southwest region.

It can be seen that with the reclamation of agricultural areas and the gradual southward migration of the Han population, the imaginary area of miasma is shrinking after the formation of one population center after another. In the 1960 s, due to the expansion of barefoot doctors and the construction of farmland water conservancy, the imagination of malaria in southwest China disappeared.

Therefore, it is inaccurate to say that miasma is a concrete thing. It should be said that it is a comprehensive concept of hypothetical environmental threats and real environmental threats.