古之至人，穷于阴阳之化，究乎生死之际，所着《内经》，悉言人以胃气为本。盖人受水谷之气以
生，所谓清气、荣气、卫气、春升之气，皆胃气之别称也。夫“胃为水谷之海”，“饮食入胃，游溢精气，
上输于脾；脾气散精，上归于肺；通调水道，下输膀胱。水精四布，五经并行，合于四时五脏阴阳，揆度
以为常也。”
苟饮食失节，寒温不适，则脾胃乃伤；喜怒忧恐，劳役过度，而损耗元气。既脾胃虚衰，元气不
足，而心火独盛。心火者，阴火也，起于下焦，其系系于心，心不主令，相火代之；相火，下焦胞络
之火，元气之贼也。火与元气不能两立，一胜则一负。脾胃气虚，则下流于肾，阴火得以乘其土位。故
脾胃之证，始得之则气高而喘，身热而烦，其脉洪大而头痛，或渴不止，皮肤不任风寒而生寒热。盖阴火
上冲，则气高而喘，身烦热，为头痛，为渴，而脉洪大；脾胃之气下流，使谷气不得升浮，是生长之令
不行，则无阳以护其荣卫，不任风寒，乃生寒热，皆脾胃之气不足所致也。
然而与外感风寒所得之证颇同而理异。内伤脾胃，乃伤其气；外感风寒，乃伤其形。伤外为有余，有
余者泻之，伤内为不足，不足者补之。汗之、下之、吐之、克之，皆泻也；温之、和之、调之、养之，皆
补也。内伤不足之病，苟误认作外感有余之病而反泻之，则虚其虚也。《难经》云∶实实虚虚，损不足而
益有余，如此死者，医杀之耳！然则奈何？曰∶惟当以甘温之剂，补其中，升其阳，甘寒以泻其火则愈。
《内经》曰∶“劳者温之”，“损者温之”。盖温能除大热，大忌苦寒之药泻胃土耳。今立补中益气汤。
The ancient sages thoroughly investigated the transformation of Yin and Yang, and exhaustively explored the boundaries of life and death. In their work, the *Huangdi Neijing* (Yellow Emperor's Inner Canon), they emphasized that humans rely on Stomach Qi (Stomach Energy) as their foundation. Essentially, humans derive life from the Qi of water and grain (food and drink). The so-called Clear Qi (Clear Energy), Ying Qi (Nutritive Energy), Wei Qi (Defensive Energy), and Spring-rising Qi are all alternative names for Stomach Qi. As stated in the text: "The Stomach is the Sea of Water and Grain." "When food and drink enter the Stomach, their essence overflows and is transported upward to the Spleen; the Spleen disperses this essence, sending it upward to return to the Lung; the Lung regulates the water passages, transporting it downward to the Bladder. The water essence distributes in four directions, and the Five Meridians run in parallel, harmonizing with the Yin and Yang of the Four Seasons and Five Zang Organs, establishing this as the standard measure for health."
If dietary habits are irregular, or if there is discomfort due to cold or heat, the Spleen and Stomach will be injured. Emotional fluctuations such as anger, joy, worry, and fear, along with excessive physical labor and fatigue, will deplete Yuan Qi (Original Energy). Once the Spleen and Stomach become weak and deficient, and Yuan Qi is insufficient, Heart Fire (Heart Heat) becomes solitary and flourishing. Heart Fire is also known as Yin Fire. It originates in the Lower Jiao (Lower Burner), its connections are tied to the Heart, but since the Heart does not issue commands, Xiang Fire (Ministerial Fire) acts on its behalf. Xiang Fire is the fire of the Lower Jiao Bao Luo (Pericardium Collaterals), and it is a thief of Yuan Qi. Fire and Yuan Qi cannot coexist; when one prevails, the other declines. When Spleen and Stomach Qi is deficient, it flows downward into the Kidneys, allowing Yin Fire to invade and occupy the Earth position (Spleen and Stomach). Therefore, in diseases of the Spleen and Stomach, initially, there is rapid breathing and panting, body heat and irritability, a洪大 (Surging-Large) pulse accompanied by headache, or unquenchable thirst, and skin unable to withstand wind-cold, resulting in aversion to cold and fever. This is because Yin Fire rushes upward, causing rapid breathing and panting, bodily irritability and heat, headache, thirst, and a Surging-Large pulse; meanwhile, Spleen and Stomach Qi flows downward, preventing Gu Qi (Grain Qi) from ascending and floating. Thus, the command of growth and generation fails to operate, leaving no Yang Qi to protect Ying Qi and Wei Qi. Unable to resist wind-cold, aversion to cold and fever arise. All these symptoms are caused by the insufficiency of Spleen and Stomach Qi.
However, these symptoms are quite similar to those caused by external contraction of wind-cold, yet the underlying principles differ. Internal injury to the Spleen and Stomach damages Qi (Energy); external contraction of wind-cold damages the Form (Body). Injury from external pathogens constitutes an Excess condition, which should be treated with draining methods; injury to internal Zheng Qi (Upright Energy) constitutes a Deficiency condition, which should be treated with tonifying methods. Sweating, purging, vomiting, and attacking are all draining methods; warming, harmonizing, regulating, and nourishing are all tonifying methods. If a disease of internal deficiency is mistakenly identified as an external excess disease and treated with draining methods, it will further weaken the deficiency. The *Nan Jing* (Classic of Difficult Issues) states: "Making the excess more excess and the deficient more deficient," damaging what is insufficient and benefiting what is already excessive—those who die in this manner are killed by the physician. So, what should be done? The answer is: One must use sweet-warm formulas to tonify the Middle Jiao (Middle Burner) and raise Yang Qi, and use sweet-cold herbs to clear the Fire, thereby achieving recovery. The *Huangdi Neijing* says: "For exhaustion, use warmth"; "For deficiency, use warmth." Warmth can eliminate great heat. It is strictly forbidden to use bitter-cold medicines to attack the Stomach Qi. Therefore, I now establish Bu Zhong Yi Qi Tang (Tonify the Middle and Augment the Qi Decoction).