Zhao Sizhen stated: The *Mingli Lun* (Theory of Clarification) mentions that alternating chills and fever is a manifestation of the struggle between pathogenic factors (Xieqi) and healthy Qi (Zhengqi). When pathogenic factors invade, if healthy Qi does not contend with them, there will be fever without chills. Only when pathogenic factors and healthy Qi engage in contention do chills and fever arise. This is because cold pathogenic factors belong to Yin, while heat pathogenic factors belong to Yang; the interior (Li) belongs to Yin, and the exterior (Biao) belongs to Yang. When pathogenic factors lodge in the exterior, if it is cold pathogenic factors contending with the Yang of the exterior, chills will manifest. When pathogenic factors enter the interior, if it is heat pathogenic factors contending with the Yin of the interior, fever will manifest. If pathogenic factors remain in the half-exterior half-interior region, contending outwardly with Yang produces chills, and contending inwardly with Yin produces fever. At this time, the distinction between exterior and interior is blurred, and internal and external manifestations are indefinite. Consequently, chills and fever come and go, occurring three to five times a day, or even more than ten times in severe cases.

If this results from the mutual overcoming of Yin and Yang Qi, insufficient Yang leads to chills followed by fever, while insufficient Yin leads to fever followed by chills. This describes the mutual overacting of Yin and Yang Qi in miscellaneous diseases and cannot be applied to Shanghan (Cold Damage). This discussion is precise and profound, aligning deeply with the intent of Zhang Zhongjing. It not only clarifies doubts but also applies to the views presented in the *Huo Ren Shu* (Book for Saving Lives).

Furthermore, according to research: Liu Wansu argued that chills indicate cold in the exterior, or that body heat with chills indicates heat in the skin and cold in the bone marrow; these are errors. The *Huo Ren Shu* also uses this as a distinction between exterior and interior. Therefore, Zhao stated: Examining Zhang Zhongjing’s discussions closely, he distinguishes only between skin and bone marrow, not using terms like exterior and interior, because skin, vessels, flesh, sinews, and bones—the five categories—are considered in the *Suwen* (Plain Questions) as the external correspondences of the Zang organs, governing the outside and filling the body. Only when referring to Zang and Fu organs can one speak of exterior and interior relationships. Thus, skin is above the bone marrow, representing the superficial external layer; bone marrow is below the skin, representing the deep internal layer. This differs from the principle where meridians belong to the exterior and Zang-Fu organs belong to the interior. Moreover, Zhang Zhongjing introduced this example at the beginning of the Taiyang chapter, clearly indicating it proves an exterior syndrome.

From this, we know that individuals who are constitutionally weak and cold, upon contracting pathogens and developing fever, have superficial heat that cannot overcome deep-seated cold; thus, they feel externally fearful of cold and desire to wear clothes. This is what is meant by "heat in the skin, cold in the bone marrow," requiring acrid-warm medications. Conversely, for robust individuals who are constitutionally hot, or those accustomed to drinking alcohol, at the initial stage of contracting pathogens, before the cold transforms into heat, Yin pathogens close off latent heat. Yin condenses on the outside, while heat accumulates inside, causing internal restlessness and aversion to clothing. This is what is meant by "cold in the skin, heat in the bone marrow," necessitating warm-cool medications. After one paroxysm, the exterior is resolved and the interior harmonizes; this is the unspoken brilliance of Zhang Zhongjing. If skin were considered the exterior and bone marrow the interior, could the joint pain seen in Mahuang Tang (Ephedra Decoction) syndromes be called both an exterior and an interior syndrome?

However, regarding Zhang Zhongjing’s *Shanghan Lun*, people generally know it as the ancestor of formula literature but fail to view it as a text from the Qin and Han dynasties. Consequently, they harbor doubts about its fundamental principles and great laws. Later generations, benefiting from its legacy, often compiled Shanghan formulas and discussions, some of which lost the original meaning or employed forced interpretations. How much more so for those who discuss miscellaneous diseases, merely citing examples?