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1. This book is specifically designed for seasonal diseases (Shi Bing). "Seasonal diseases" refer to conditions caused by the pathogenic influence of the six Qi (Wind, Cold, Summer-heat, Dampness, Dryness, Fire) of the four seasons, not referring to "epidemic diseases" (Shi Yi). Therefore, this book exclusively discusses diseases of the four seasons and does not include any warm epidemics. In years when plagues occur, one may refer to Mr. Wu Keyou's works; there is no need to repeat them here.

2. All discussions in this book are based on the *Huangdi Neijing* (Yellow Emperor's Inner Canon) and the theories of past sages, without any fabrication. However, some sections first adopt a theory and later discard its prescription, or first refute its bias but retain its method. This is not due to skepticism, but rather to select the good and follow it. Even if I, Lei Feng, have occasional insights, I will record them clearly so that readers understand at a glance, thereby expressing my intent to seek correction from experts.

3. All treatment methods presented are proposed by me, modeled after ancient prescriptions with slight modifications. The herbs used have been carefully studied and researched; I dare not use them arbitrarily to avoid harming patients. After each method, detailed explanations are provided so that students understand the specific utility of each herb.

4. All formulas are selected from the works of past philosophers to supplement the limitations of various methods. Some of these involve excessive sweating, excessive purging, excessive cold, or excessive heat. It is necessary to append my comments afterwards. This is not out of arrogance to criticize ancients, but out of fear that students might rigidly apply ancient formulas to contemporary diseases without flexible adaptation, leading to ridicule for being inflexible ("gluing the tuning pegs").

5. The medical cases recorded are those documented during my clinical practice. Observing ancient case records, they mostly describe critical illnesses and rarely mild ones. One should realize that mild conditions are often the precursors to critical ones. Thus, the Sages taught not to neglect details and to be cautious of subtle signs. Therefore, both critical and mild cases are recorded to enable doctors and patients to prevent problems before they arise and stop them from growing.

6. This book takes eight lines from the *Da Lun Yin Yang Ying Xiang* (Great Treatise on the Correspondence of Yin and Yang) in the *Neijing* as its outline, collecting diseases caused by the six Qi of the four seasons as items. Generally speaking, it traces the source of the ancient sages; specifically, it discusses the foundation of later scholars. Other discussions are attached at the end of the volume.

The classic states: "If one is injured by Cold in winter, one will inevitably suffer from Warmth in spring." This instructs us that diseases can be caused by latent Qi (Fu Qi). If injured by Cold in winter and the illness manifests immediately, it is called Shanghan (Cold Damage). If mild and not immediate, the pathogenic factor lies dormant in the skin and muscles, or in the Shaoyin channel. When Yang Qi opens and disperses in spring, an external pathogen may trigger the latent Qi, causing disease onset. Occasionally, it may also arise spontaneously without external triggering. Those with latent factors in the skin and muscles are usually those who labored and sweated during winter activities. Those with latent factors in the Shaoyin are usually those who failed to conserve Jing (Essence) in winter, resulting in Kidney deficiency. As the ancients said, "The most deficient place is where pathogens reside." Why do figures like Liu Songfeng and Chen Pingbo deny the existence of latent Qi? They commit the sin of contradicting the classics; how can they escape blame? According to my analysis, there are five types of latent Qi in spring: Chunwen (Spring Warmth), Fengwen (Wind Warmth), Wenbing (Warm Disease), Wendu (Warm Toxicity), and Wanfa (Late Onset).
- Chunwen arises from slight Cold acquired in winter, triggered by Cold sensation in spring.
- Fengwen also arises from slight Cold acquired in winter, triggered by Wind sensation in spring.
- Wenbing arises from slight Cold acquired in winter, which ferments into Heat. When Yang Qi expands in spring, the latent Qi erupts internally without needing Cold or Wind triggers.
- Wendu arises from aberrant Qi acquired in winter. At the transition between spring and summer, influenced by Warmth, latent toxicity erupts internally.
- Wanfa arises from slight Cold acquired in winter, which did not manifest initially but appears after the Qingming solar term, occurring one stage later than typical Warm Diseases.
These five types all result from Winter Cold injury, lying dormant until spring, forming various Warm Diseases. They must be differentiated and treated separately.

Cheng Xi stated: "Regarding Liu Songfeng and Chen Pingbo's denial of latent Qi, their reasoning has origins. One clings to the phrase 'Winter injury by sweat' from *Yunji Qiqian*, and the other to Qian Yi's text regarding 'Winter Cold injuring the Water organ.' Neither side considers only half the argument, completely ignoring the teachings on Spring, Summer, and Autumn injuries. How should these be interpreted? Although these two gentlemen possessed high intellectual capacity, they were misled. If we do not correct their errors but instead support their views, it is no wonder later physicians uniformly attribute such cases to sudden external contraction (Bao Gan), recklessly using dispersing agents like Qianghuo, Fangfeng, Mahuang, and Guizhi to force sweating and deplete Jin-Ye (Body Fluids), thereby endangering lives. This is inevitable, and the blame must fall on the originators of these erroneous theories."