(The relevant discussions can be found in the general examples at the beginning of this book.)

(Winter cold damage is called Shanghan (Cold Damage); spring warm disease is called Wenbing (Warm Disease); summer heat disease is called Shubing (Summer Heat Disease); autumn malaria is called Nue (Malaria); when people of all ages suffer from similar illnesses within a year, it is called Yi (Epidemic); excessive sleepiness, profuse sweating, and floating pulse are called Fengwen (Wind-Warmth); whole-body pain is called Shi (Dampness); body opisthotonos is called Jing (Spasm).)

Wu Kun stated: The disease of Shanghan (Cold Damage) occurs when one contracts cold pathogenic factors immediately after the Frost Descent solar term due to severe cold weather; this is truly Shanghan. If one contracts pathogens during warm weather, it is called Dongwen (Winter Warmth). When spring arrives and the weather is warm, if someone suffers from high fever, this is Wenbing (Warm Disease). If the weather remains cold with ice and snow unmelting, and one contracts cold, it is also termed Shanghan. Between the third month and July or August, if there is a sudden cold snap and one contracts it, this is named Shixing Hanyi (Seasonal Cold Epidemic). After the Summer Solstice, if one presents with high fever and a surging pulse, it is called Rebing (Heat Disease). If the climate of the four seasons is abnormal, causing illness that spreads among people of all ages similarly, it is called Shixing Zhiqi (Seasonal Pathogenic Qi). This "Shixing" is also known as Shiyi (Seasonal Epidemic), caused by contracting epidemic pestilential qi from heaven and earth, which is not cold in nature. There are also conditions such as Wen Nue (Warm Malaria), Fengwen (Wind-Warmth), Wendu (Warm Toxin), Wenyi (Warm Epidemic), Zhongfeng (Stroke/Attack by Wind), Shangfeng (Injury by Wind), Zhongshi (Attack by Dampness), Fengshi (Wind-Dampness), Zhongshu (Attack by Summer Heat), and Zhong Wenwen (Attack by Warm-Dampness). All these present with fever and resemble Shanghan; thus, physicians generally refer to them as Shanghan because their fever and progression are similar. However, the medication differs, specifically in the methods of releasing the exterior and resolving the muscle layer.

Shanghan in winter refers to illness occurring immediately upon exposure to cold. If it does not occur immediately, it transforms into Wenbing in spring and Rebing in summer. Wenbing and Rebing result from latent cold transforming; once transformed, it can no longer be considered cold. Shixing Hanyi involves sudden cold weather compared to the severe cold of winter, differing in severity. Shixing Zhiqi is naturally the epidemic qi circulating in the heavens and earth, distinct from cold. Wenbing arises from vapors of mountains and marshes; Shubing arises from the fire-wind of scorching suns; these are "thieves of heaven" harming humans. Some cases are severe, others mild. Wen Nue and Fengwen are often complications (Huai Zheng) of mismanaged Shanghan, changed by contracting different pathogens, each having distinct causes. How can they all be indiscriminately treated as Shanghan? If one fails to recognize these names and treats blindly—for example, treating Zhongshu (Summer Heat Attack) as Rebing, or Zhong Wenwen as Fengwen—one confuses deficiency and excess, creating chaos and shortening life. Must one not be cautious?

Generally, for Shanghan in the four seasons, supplementation combined with dispersal is appropriate. Therefore, Zhu Danxi treated Shanghan mostly using Buzhong Yiqi Tang (Tonify the Middle and Augment the Qi Decoction); for Qi deficiency, Sijunzi Tang (Four Gentlemen Decoction) plus dispersing agents was used; for Blood deficiency, Siwu Tang (Four Substances Decoction) plus dispersing agents was used. Li Dongyuan treated Fengshi (Wind-Dampness) using Buzhong Yiqi Tang plus Qianghuo (Notopterygii Rhizoma et Radix), Fangfeng (Saposhnikoviae Radix), Shengma (Cimicifugae Rhizoma), and Bencaozhu (Atractylodis Chinensis Rhizoma). Wang Haizang treated wind-dampness without sweat using Shenzhu Tang (Divine Skill Decoction) and with sweat using Baizhu Tang (Atractylodes Macrocephala Decoction); for Gangjing (Stiff Spasm), he used Shenzhu Tang plus Qianghuo and Mahuang (Ephedrae Herba); for Roujing (Flaccid Spasm), he used Baizhu Tang plus Guixin (Cinnamomi Cortex) and Baizhu (Atractylodis Macrocephalae Rhizoma); for wind-dampness, he used Baizhu Tang modified according to symptoms; for dampness attack with wiry, fine, hollow, or slow pulses, he used Huangqi Tang (Astragali Decoction). These align with Zhang Zhongjing's principles regarding Shanghan contracted by hardworking individuals exposed to pathogens.

Zhang Zhongjing discussed Shanghan but did not address Zhonghan (Cold Attack). Ancients treated Zhonghan characterized by fainting due to exposure to extreme cold using Fuzi Lizhong Tang (Aconite Decoction to Regulate the Middle). Their pharmacological reasoning was sound, yet they did not discuss the differences between "Shang" (Injury) and "Zhong" (Attack). Shanghan may manifest immediately or be delayed. Due to pre-existing internal stagnation of heat, external wind-cold constrains the skin and pores, trapping heat which then manifests as a heat disease, entering meridians gradually and deepening. Initially, mild diaphoresis with Mahuang or Guizhi (Cinnamomi Ramulus) suffices because the body is not significantly deficient. In contrast, Zhonghan results from sudden contraction of cold; the disease manifests abruptly and violently. Because the pores are open and the whole body is affected, meridian differentiation is difficult, and there is typically no fever; warming and tonification are required for resolution. This indicates severe deficiency of Qi; without urgent treatment, death ensues. Shangfeng (Wind Injury), Shangshu (Summer Heat Injury), and Shangshi (Dampness Injury) progress gradually like Shanghan. Zhongfeng (Wind Attack), Zhongshu (Summer Heat Attack), and Zhongshi (Dampness Attack) occur suddenly like Zhonghan. Beyond Shanghan, treatments for miscellaneous diseases can be inferred by analogy.]