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The disease of malaria (Malaria) originates from external pathogenic factors; therefore, the *Neijing* (Classic of Internal Medicine) discusses malaria solely in terms of wind (Wind) and cold (Cold), which is quite clear. However, discussions in later generations have been inconsistent and chaotic, generally summarizing only the superficial manifestations while losing sight of the root cause. Consequently, the more debates there are, the more obscure the condition becomes. There is a detailed analysis following this passage that should be examined together.

Everyone knows that malaria can be caused by summerheat (Summerheat). However, they fail to realize that the intense heat of summer is naturally suitable for the body's healthy qi (Healthy Qi). Nevertheless, some individuals fear the heat and seek shade or cool places, indulging excessively in cooling behaviors. This results in contracting cold (Cold) due to summerheat exposure, thereby leading to malaria. The classics state: "Those who do not sweat during the summer heat will develop wind-malaria (Wind-Malaria) in autumn," the meaning of which can be inferred. Yet, it is primarily those with weak constitutions or excessive fatigue and injury who are particularly susceptible to pathogens. This explains why the depth of pathogenic invasion varies, resulting in differences in disease severity. Although the etiology is attributed to summerheat, one must understand that summerheat has yin and yang aspects; malaria specifically arises from yin-summerheat (Yin Summerheat). Regarding pathological changes, some present as cold syndromes (Cold Syndrome), others as heat syndromes (Heat Syndrome); some require dispersing methods (Dispersing Method), others astringent methods (Astringent Method); some need warming (Warming Method), and others clearing (Clearing Heat Method). The key lies in the four characters: root and branch (Root and Branch), deficiency and excess (Deficiency and Excess). Understanding these four aspects allows for appropriate treatment based on the syndrome, achieving perfection. Those who claim summerheat injury but equate summerheat with fire (Fire), or those who attribute spleen cold (Spleen Cold) and rigidly insist on all cases being cold, hold one-sided views that are unreliable.

Malaria occurring after the Summer Solstice and before the Autumn Equinox involves the yang aspect (Yang Aspect) and indicates a shallow disease; occurring after the Autumn Equinox and before the Winter Solstice involves the yin aspect (Yin Aspect) and indicates a deep disease. Onset between Zi hour (23:00–01:00) and Wu hour (11:00–13:00) indicates a yang aspect disease, which is easier to cure; onset between Wu hour and Zi hour indicates a yin aspect disease, which is difficult to cure. Shallow diseases manifest daily; deep diseases manifest every other day. If the interval is three or four days, it is because the pathogen has remained for a long time and resides in the yin aspect, indicating an even deeper disease.

When malaria shifts gradually from yin to yang, and from longer intervals to shorter intervals of onset, it indicates a transition from severe to mild. Conversely, shifting from yang to yin, and from shorter to longer intervals, indicates a transition from mild to severe. When the pathogenic factor is extremely deep, the onset is necessarily delayed, often resulting in every-other-day episodes. It is a favorable sign only when the onset gradually advances and the intervals shorten. Therefore, treating this disease is easier in spring and summer, and more difficult in autumn and winter.