(This section is a first draft, so Zhang Zhongjing's methods are mixed with later successors' methods. Since it is quite logical, no corrections are made; readers should examine it carefully.)

Chills (Ehan) refer to wind-cold pathogens lodging in the Ying and Wei levels. It is not the "cold" aspect of alternating chills and fever, nor is it aversion to wind. Therefore, one does not need to be exposed to wind to feel afraid of cold; even with high body heat, there is no desire to remove clothing or bedding. In severe cases, even approaching fire or adding quilts cannot suppress the cold sensation. This occurs because Yin qi ascends into the Yang region, or due to deficient Yang, or the interplay between wind pathogen and deficiency. Chills generally belong to Exterior syndromes. Even if Interior symptoms are fully present, if there is slight chills, the Exterior syndrome has not resolved and must be treated first. Only when chills cease can Interior excess be purged. The Classic states: "Fever with chills indicates onset from Yang meridians; sweating may be used."

Absence of fever with chills, curling up, and a deep, fine pulse indicate onset from Yin meridians; warming the Interior is appropriate. Although chills all belong to the Exterior, they have Deficiency and Excess distinctions. Sweating with chills indicates Exterior Deficiency; non-sweating with chills indicates Exterior Excess. Exterior Deficiency can be treated by harmonizing the muscle layer; Exterior Excess can be treated by inducing sweating.

In Shanghan (Cold Damage), Taiyang disease is at the Exterior, hence chills; Shaoyang disease is half-Exterior and half-Interior, hence slight chills; Yangming disease is at the Interior and normally has no chills. If chills occur, it is a concurrent disease with Taiyang.

Taiyang: Chills, fever, floating pulse. (Formula discussion see previous section on "Taiyang Disease Fever").

Yangming: Wind-stroke with bitter taste, dry throat, abdominal fullness, slight wheezing, fever, chills, floating-tight pulse—this is also an indication for Mahuang Tang (Ephedra Decoction). Yangming disease with slow pulse, profuse sweating, and slight chills indicates unresolved Exterior syndrome, which is also an indication for Guizhi Tang (Cinnamon Twig Decoction). (In hot seasons, substitute herbs as per previous examples.)

Shaoyang: Head sweating, slight chills—treat with Xiaochaihu Tang plus Guizhi (Minor Bupleurum Decoction plus Cinnamon Twig).

Three Yin Diseases: Only Shaoyin meridian presents with chills; Taiyin and Jueyin do not. However, Shaoyin chills have two presentations: Onset in Shaoyin presents with no fever and chills, suitable for warming methods, belonging to Lizhong Tang (Regulate the Middle Decoction) or Sini Tang (Frigid Extremities Decoction). Shaoyin no-fever chills resemble the earlier Taiyang case where heat does not immediately appear. "Cold without immediate heat" refers to Taiyang signs being complete but heat not yet manifest. Here, "no-fever chills" implies absence of Taiyang headache, identifying it as Shaoyin.

Shaoyin disease: Diarrhea, chills, and curling up—treat with Sini Tang, Zhenwu Tang (True Warrior Decoction), or Xiao Jianzhong Tang (Minor Construct the Middle Decoction). If chills and curling up are accompanied by occasional restlessness and desire to remove bedding, *Ren Shu* suggests using Daxiehu Tang (Major Bupleurum Decoction) to purge. Zhao believes warming dispersal of Yin pathogen and guiding True Yang out via sweating is appropriate. Purging would not resolve the Exterior but further weaken the Interior, allowing chills pathogen to sink inward. Even if the pulse is deep, slippery, and excess, Daxiehu Tang should not be used hastily. First resolve the Exterior until chills cease. Shaoyin disease with chills, curling up, diarrhea, and cold extremities is incurable (due to lack of Yang). Shaoyin Sini with chills, curling up, absent pulse, no irritability but agitation is fatal.

Exteriorly, Taiyin spontaneous diarrhea without thirst, and Jueyin diarrhea with cold extremities, may both present with chills. Taiyin suits Lizhong Tang; Jueyin suits Sini Tang. Previously stated that Two Yins do not have chills, now stating they may. Note: Taiyin and Jueyin do not have chills when Yang transmits to Yin; Three Yins can have chills when Yin enters Yin, especially frequent in Shaoyin. Chills, faint pulse, followed by diarrhea cessation indicating blood loss—treat with Sini Tang plus Renshen (Ginseng). (Cheng Wuji notes: Chills, faint pulse, and diarrhea indicate Yang deficiency and Yin excess. Cessation of diarrhea means internal exhaustion of fluids, hence "blood loss." *Jinkui Yufan* states: When water dries, blood is absent. Use Sini Tang to warm meridians and assist Yang, add Renshen to generate fluids and benefit blood.)

Sini Tang plus Renshen Formula:
Renshen (Ginseng Root), Ganjiang (Dried Ginger Rhizome), Gancao (Licorice Root, prepared) (each 1 liang); Fuzi (Aconite Lateral Root, processed, peeled, roasted) (1 piece). Coarsely powder. Take 5 qian per dose, decoct in water, take warm, three times daily.

After sweating, if disease persists and chills worsen, it is deficiency. Treat with Shaoyao Gancao Fuzi Tang (Peony, Licorice, and Aconite Decoction). (Cheng Wuji notes: After sweating, if disease resolves, no chills. If disease persists and Exterior is excess, no chills. Now, disease persists and chills worsen, indicating Ying and Wei both deficient. Sweating depletes Ying; chills deplete Wei. Give Shaoyao Gancao Fuzi Tang to tonify Ying and Wei.)

Shaoyao Gancao Fuzi Tang Formula:
Shaoyao (Peony Root), Zhigancao (Prepared Licorice Root) (each 3 liang); Fuzi (Aconite Lateral Root, processed, peeled, broken into 8 pieces) (1 piece). These three ingredients, decoct in 5 sheng of water to obtain 1.5 sheng. Strain, divide into warm doses. Suspected not to be Zhang Zhongjing's original intent. (Cheng Wuji notes: Shaoyao's sour nature astringes fluids and benefits Ying; Fuzi's pungent-hot nature secures Yang and benefits Wei; Gancao's sweet nature harmonizes sour and pungent and stabilizes Zheng Qi.)

After purging and then sweating, trembling chills, faint-fine pulse indicate interior and exterior deficiency. Treat with Danggui Sini Tang (Angelica Sinensis Decoction for Cold Extremities) or Zhenwu Tang.

Taiyang disease after purging, rapid pulse, chest fullness—treat with Guizhi Qu Shaoyao Tang (Cinnamon Twig Decoction minus Peony).

Guizhi Qu Shaoyao Tang Formula:
Guizhi (Cinnamon Twig, bark removed), Shengjiang (Fresh Ginger Slice) (each 1.5 liang), Zhigancao (Prepared Licorice Root) (1 liang), Dazao (Jujube Fruit) (6 pieces). Coarsely powder. Take 5 qian per dose, decoct in water, take warm. If slight chills, treat with Guizhi Qu Shaoyao Fuzi Tang (Cinnamon Twig Decoction minus Peony plus Aconite). (Add half a piece of peeled, processed Fuzi to the previous formula. *Ren Shu* says: Shaoyao is sour; rapid pulse and chest fullness fear forming Jie Xiong (Chest Binding). Thus, use only pungent-sweet flavors to disperse toxins.)

After sweating or purging in Shanghan, epigastric stuffiness with chills indicates unresolved Exterior. First use Guizhi Tang to resolve Exterior, then Dahuang Huanglian Xiexin Tang (Rhubarb, Coptis, and Scutellaria Heart-Purging Decoction) to attack stuffiness. If stuffiness with sweating and chills, Exterior is resolved. Treat with Fuzi Xiexin Tang (Aconite Heart-Purging Decoction). (Formula discussion see "Pi/Stuffiness" section.)

Back Chills (Bei Ehan): Back belongs to Yang, Front to Yin. Back cold indicates weak Yang. There are two Yin-Yang presentations. One Shaoyin presentation: Yin-cold pathogen is excessive, failing to consume fluids, so mouth feels normal. One San Yang combined disease presentation: Yang sinks, fluids dry up, so tongue is dry and mouth parched. Distinguish by this. Mouth normal with back chills belongs to Shaoyin, suitable for Fuzi Tang (see "Sleepiness/Lethargy"). Tongue dry, mouth parched, Internal Heat signs, mouth numbness, back chills belong to San Yang combined disease, suitable for Baihu Tang (White Tiger Decoction) (see "Fever"). Classic states: Abdominal fullness, heavy body, greasy face, delirium, urinary incontinence, mouth numbness—San Yang combined disease, treat with Baihu Jia Renshen Tang (White Tiger Plus Ginseng Decoction) (see "Thirst"). If spontaneous sweating, also use Baihu Jia Renshen Tang. Additionally, Yangming syndrome with slight back chills, no high fever, dry mouth/thirst—also use Baihu Jia Renshen Tang. Summerheat also presents with back chills, but with greasy face, spontaneous sweating, empty-depressed pulse; see Miscellaneous Diseases. For those with inherent Spleen-Stomach deficiency, drinking cold water/ice or eating raw/cold food in summer causes cold accumulation, Yin attacks Yang, so cold rises from the back, cold like palm size. Treat with warming medicines (such as Dashun San).