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[Invention]

Regarding the etiology of Shanghan (Cold Damage), all arguments stem from a single chapter titled "Re Lun" (Discourse on Heat). The core viewpoint is that Shanghan transmits only through the Foot meridians and not the Hand meridians. Why is this? Because Shanghan disease is contracted in winter. The Foot Taiyang Bladder Meridian is the initial meridian affected, and the Foot Jueyin Liver Meridian is the terminal one. This disease primarily injures the North (Kidney) and East (Liver), as well as specific positions associated with Dampness of the Foot Yangming Stomach at Xu Earth and Spleen Earth at Chou Earth. Generally, the six Foot meridians are located in the Northeast direction. The classic states: "If cold is injured in winter and manifests immediately, it is called Shanghan; if it manifests in spring, it is called Warm Disease; if it manifests in summer, it is called Warm Epidemic." This represents the most severe form of illness. Zhang Zhongjing stated, "Without the Extraordinary Vessels, there would be no Shanghan," because the Extraordinary Vessels attach to the six Foot meridians but not the Hand meridians. Cold pathogens only injure the Foot meridians due to the presence of the Extraordinary Vessels. In late summer, major heat diseases occur because Fire Qi dominates in summer. The direction of Fire and the boundary with Autumn are where the Hand meridians reside; the direction of Water and the boundary with Spring are where the Foot meridians reside. If Summer Fire Qi is dominant, external pathogens assist the Hand meridians, causing the already deficient meridians to become even more deficient. Therefore, the medications used are those that drain excess rather than targeting the Foot meridians. Why drain excess? Because draining the excess replenishes the deficiency. This explains why Shanghan is described as transmitting first through the Foot meridians without mentioning the Hand meridians. The general idea is as above. However, transmission to the Hand meridians does occur.

[Ci Shi Nan Zhi - Difficulties in Understanding This Matter]

Question: When Shanghan reaches the fifth or sixth day, symptoms gradually change to mental confusion, muteness, or speaking alone in sleep for one or two sentences. The eyes are red, lips are cracked, tongue is dry, yet there is no desire to drink water. Thin porridge can be swallowed if offered, but if not offered all day, there is no desire to eat. The pulse is fine and rapid but not surging. There is no epigastric fullness or abdominal distension, and urination and defecation are normal. Or, after ten days, the patient appears intoxicated, suffering from persistent false mental confusion. Using Chengqi Tang (Gut-Draining Decoction) to purge in such cases is an error. This is due to ignorance that the heat has transmitted to the Hand Shaoyin Heart Meridian. Furthermore, it is unknown which meridian it came from.

Answer: Originally, the Taiyang meridian was injured by Wind. Wind is a Yang pathogen; Yang pathogens injure Wei (Defensive) Qi, causing Yin Blood to naturally dry up. Heat accumulates in the Bladder (Ren Water) and reversely transmits to Bing Fire (Small Intestine). Bing and Ding are like siblings, thus transmitting to the Heart. Heart Fire presses down from above and steams the Lung, causing mental confusion. The Lung is a clear and empty organ; internal fire causes this confusion. It is appropriate to use Zhizi Huangqin Huanglian Tang (Gardenia, Scutellaria, and Coptis Decoction). If the pulse indicates pathology in Bing (Small Intestine), use Daochi San (Guide Out Red Powder); if in Ding (Heart), use Xiexin Tang (Drain the Heart Decoction). If mistakenly using Liangge San (Cooling the Chest Powder), which treats blood within the Qi level, it would be incorrect. If the Cun position on the left hand is deep, slippery, and forceful, it may be used. Alternatively, Xijiao Dihuang Tang (Rhinoceros Horn and Rehmannia Decoction) is also close to this indication. The original formula states that if Rhinoceros Horn is unavailable, Shengma (Cimicifugae Rhizoma) can substitute it; this is a Yangming meridian herb that clears heat from the blood in the Yangming meridian. If the pulse is forceful in both floating and deep positions, it indicates heat in both Bing and Ding. Taking half doses of Daochi San and Xiexin Tang together would be appropriate. This syndrome involves transmission from Bladder to Bing, from Foot to Hand meridians, from lower to upper, from Bing to Ding, from exterior to interior. Ren transmitting to Ding is analogous to Gen transmitting to Li, known as transcending meridian transmission, or Fu (Hollow Organ) transmitting to Zang (Solid Organ). Zhu Gong (author of Huo Ren) stated, "Shanghan transmits only through Foot meridians, not Hand meridians." This statement is incomplete. There are cases of transmission from Foot to Hand meridians. How do we know? The classics state: "Transmission of cold may affect only one meridian or skip three meridians." One cannot rely on a single rigid method. Treatment must depend on the pulse and external symptoms; this is the flexible approach. Swallowing food indicates the pathogen is not in the Stomach; lack of desire to eat when not offered is due to mental confusion. Since the heat is not in the Stomach, mistakenly using Chengqi Tang to purge will inevitably lead to death.

[Commentary]

Comment: Shanghan originally transmits only through the Foot meridians; the above examples illustrate the principle of transmission to Hand meridians, revealing the secrets of pathogenesis. This generally occurs because pathogens accumulate over time; since the Foot meridians are full/excess and the Hand meridians are deficient,郁热 (stagnant heat) arises. Transmission may result from errors in sweating or purging, or from emotional disturbances or fatigue. Generally, transmission to a specific meridian always has a cause. Thus, ancient physicians employed methods such as Niujie (Rescuing Reversal) and Fumai (Restoring Pulse), not merely addressing symptoms but also inspiring future generations' understanding.