气无形而血有质，气为阳，主护卫于外，故名之曰卫；血为阴，主营运于中，
故名之曰营。血阴有质，故其行也必次第循经，而入于脉道之中，充于内而后达于
外。气阳无形，故其行也 疾，不循经而出于脉道之外，实于表而后返于里。观（《内经》
谓饮酒者，气先行皮肤，先充在外之络脉，而后满于在内之经脉。可见矣。）此二者之行，
所以有不同也。（《经》谓营气之行，寅时起，由肺经而大肠、胃、脾、心、小肠、膀胱、
肾、心包、三焦、胆、肝诸经，复返于肺，如是者每日五十周。卫气之行，每日早至暮，
行阳分二十五周，每周由太阳而少阳、阳明、足少阴，复返于太阳。暮至晓，行阴分二十
五周，每周由肾而心、肺、肝、脾，复返于肾。二者之行不同如此。按《经》言营气，是言
血中之气，非单言血，盖血中之气，既负血而行，则亦不及卫气之 疾也。）《经》言卫气，
昼行阳二十五度，（度，即遍也。）夜行阴二十五度，大概如此。盖昼则阳动，而气行于表者多，夜
则阴静，而气敛于内者多，非昼全不行于内，夜全不行于外也。至谓一昼夜必行五
十周，则凿矣。气一耳，以其行于脉外，则曰卫气，行于脉中，则曰营气，聚于胸
中，则曰宗气。名虽有三，气本无二。气与血并根柢于先天，而长养于后天。
《经》谓营气出于中焦。又谓心生血。不过以胃受谷气，蒸化成血，血色之赤，禀于心火
为言耳。要之血即天一之水，（观血味咸可知。）气为坎中之阳，同根于肾，无岐出也。气
根于肾，亦归于肾，故曰肾纳气，其息深深。（气不归元，则喘咳不得卧。）肺司呼吸，气之
出入，于是乎主之。且气上升，至肺而极，升极则降，由肺而降，故曰肺为气主。
肾主纳气，故丹田为下气海；肺为气主，故胸中为上气海。肾水为坎中之阳所蒸，
则成气，上腾至肺，所谓精化为气，地气上为云也。气归于肺，复化为水，肺布水
精，下输膀胱，五经并行。（水之精者行于经永。）所谓水出高源，天气下为雨也。阴阳互根，
于此可悟矣。肾以闭藏为职，虽子半阳生，而气发渊泉，机犹未畅，故气之升发，
不属肾而属肝也。藏属肾，泄属肝，（升则泄矣。）此肝肾之分也。肝主升，肺主降，此
肺肝之分也。心主动，（志壹则动气也。）肾主静，此心肾之分也。而静藏不致于枯寂，
动泄不致于耗散，升而不致于浮越，降而不致于沉陷，则属之脾，中和之德之所主
也。然则升降动静，苟失其中，虽为肝、肺、心、肾之不职，亦即脾之不职。而但
知气之不升，或有升无降，为肝木克脾土者，陋也。知各脏之病，皆关乎脾，
则知脾气调和，即各脏俱调和矣。故补脾不如补肾，不过举要之词，故不若补肾不
如补脾之论，为得其全也。老人、小儿尤以脾胃为主。《经》言阳之气，以天地之疾
风名之。又曰风气通于肝，故气病往往称风，如肝风、肠风、胃风之类，（饮食在胃，则胃
实肠虚，气下于肠，饮食在肠，则肠实胃虚，气上于胃，往来鼓动有声，所谓肠风、胃风即此。）皆气之往来，
鼓动若风耳，非必外来之风也。以上明气之理，至其病证脉治，详下。
气没有形体而血有实质，气属于阳，主要在外周起护卫作用，所以称它为卫气；血属于阴，主要在内部起营养运行作用，所以称它为营气。血属阴且有形质，所以它的运行必然按照次序沿着经脉进行，进入脉道之中，充盈于体内然后通达于体表。气属阳且无形体，所以它的运行迅速，不沿着经脉而行而出现在脉道之外，充实于体表然后返回体内。观察《内经》所说的饮酒者，气先行于皮肤，先充盈在外的络脉，然后才充满在内的经脉，就可以明白这一点。（《黄帝内经》说营气的运行，从寅时开始，由肺经传至大肠、胃、脾、心、小肠、膀胱、肾、心包、三焦、胆、肝等经脉，再返回到肺，像这样每天循环五十周。卫气的运行，从早到晚，行于阳分二十五周，每周由太阳经传至少阳、阳明、足少阴经，再返回太阳经。从晚到晨，行于阴分二十五周，每周由肾传至心、肺、肝、脾，再返回肾。两者的运行如此不同。按《内经》所言营气，是指血中的气，并非单指血，因为血中的气既依附血而行，那么其速度也不及卫气之迅速。）《内经》说卫气，白天行于阳分二十五度，（度，即遍数。）夜晚行于阴分二十五度，大体上是这样。大概白天阳气发动，气多行于体表；夜晚阴气静止，气多收敛于体内，并不是白天完全不在体内运行，夜晚完全不在体表运行。至于说一昼夜必须运行五十周，那就太牵强了。气只有一种，因为它行于脉外，就称为卫气；行于脉中，就称为营气；聚积于胸中，就称为宗气。名称虽然有三个，但气的本质并没有两个。气和血都根源于先天，并依靠后天滋养。《内经》说营气产生于中焦。又说心生血。这不过是以胃受纳谷气，蒸腾化生为血，血色之赤，禀受于心火而言罢了。总之，血就是天一之水，（看血的味咸可知。）气是坎卦中的阳，同源于肾，没有分歧。气根于肾，也归于肾，所以说肾纳气，呼吸深沉。（如果气不归元，就会喘咳不能平卧。）肺主管呼吸，气的出入，由此主宰。而且气上升，到达肺部达到极点，升极则降，由肺而降，所以说肺为气之主。肾主纳气，所以丹田为下气海；肺为气之主，所以胸中为上气海。肾水被坎中之阳所蒸腾，则化为气，向上腾达至肺，这就是所谓精化为气，地气上升变为云。气归于肺，又化为水，肺布散水精，向下输送到膀胱，五脏经脉并行。（水的精华行于经脉之中。）这就是所谓水出高源，天气下降变为雨。阴阳互根的道理，从这里可以领悟了。肾以闭藏为职能，虽然子时阳气初生，气发源于深渊泉眼，但生机尚未通畅，所以气的升发，不属于肾而属于肝。脏的闭藏属于肾，泄的升发属于肝，（升即是泄。）这是肝肾的区别。肝主升，肺主降，这是肺肝的区别。心主动，（意志专一则能调动气。）肾主静，这是心肾的区别。而静藏不至于枯寂，动泄不至于耗散，升不至于浮越，降不至于沉陷，这就归属于脾，这是中和之德所主宰的。既然如此，升降动静如果失去中和，即使是肝、肺、心、肾失职，也就是脾失职。只知道气不升，或者有升无降，认为是肝木克伐脾土的，见识浅陋。知道各脏的疾病都与脾有关，就知道脾气调和，那么各脏也就都调和了。所以说补脾不如补肾，不过是一句举要的话，所以不如“补肾不如补脾”的说法，更为全面。老人、小儿尤其以脾胃为主。《内经》说阳之气，用天地的疾风来命名它。又说风气通于肝，所以气病往往称为风，如肝风、肠风、胃风之类，（饮食在胃，则胃实肠虚，气下行于肠；饮食在肠，则肠实胃虚，气上行于胃，往来鼓动有声，所谓的肠风、胃风就是这个意思。）都是气的往来鼓动像风罢了，不一定是外来的风邪。以上阐明气的道理，至于疾病的证候、脉象和治疗，详见下文。
Qi is formless, whereas blood has substance. Qi belongs to Yang and primarily guards the exterior; therefore, it is named Wei Qi (Defensive Qi). Blood belongs to Yin and primarily nourishes and circulates within; therefore, it is named Ying Qi (Nutritive Qi). As blood is Yin and has physical substance, its movement must follow a sequence along the meridians, entering the vessel channels, filling the interior before reaching the exterior. Qi is Yang and formless; thus, its movement is rapid, not following the meridians but exiting outside the vessel channels, filling the exterior before returning to the interior. Observing that *Huangdi Neijing* (The Yellow Emperor's Classic of Internal Medicine) states that for those who drink wine, Qi first moves through the skin, first filling the collateral vessels on the outside, and only then fills the main meridians inside, this distinction becomes clear. (*Huangdi Neijing* states that the circulation of Ying Qi begins at Yin hour, moving from the Lung Meridian to the Large Intestine, Stomach, Spleen, Heart, Small Intestine, Bladder, Kidney, Pericardium, Sanjiao (Triple Burner), Gallbladder, and Liver meridians, before returning to the Lung, completing fifty cycles daily. The circulation of Wei Qi moves through the Yang aspects twenty-five times from morning to evening, each cycle progressing from Taiyang to Shaoyang, Yangming, and Foot-Shaoyin meridians, returning to Taiyang. From evening to morning, it moves through the Yin aspects twenty-five times, each cycle progressing from the Kidney to the Heart, Lung, Liver, and Spleen, returning to the Kidney. Their movements differ as described. According to *Jing* (Classics), when referring to Ying Qi, it speaks of the Qi within the blood, not merely blood itself. Since the Qi within the blood travels with the blood, its speed cannot be as rapid as that of Wei Qi.) *Jing* states that Wei Qi travels through the Yang aspects twenty-five times during the day, and through the Yin aspects twenty-five times at night, generally speaking. This is because during the day, Yang is active, and Qi moves predominantly in the exterior; at night, Yin is quiet, and Qi converges predominantly in the interior. It does not mean that Qi completely fails to move in the interior during the day or completely fails to move in the exterior at night. However, claiming that it must complete exactly fifty cycles in one day and night is overly rigid. There is only one Qi. Because it moves outside the vessels, it is called Wei Qi; because it moves inside the vessels, it is called Ying Qi; because it gathers in the chest, it is called Zong Qi (Gathering Qi). Although there are three names, the essence of Qi is singular. Both Qi and Blood are rooted in Pre-heaven (Innate Constitution) and nurtured by Post-heaven (Acquired Constitution). *Jing* states that Ying Qi originates from the Middle Jiao (Middle Burner). It also states that the Heart generates blood. This merely refers to the fact that the Stomach receives grain qi, steams and transforms it into blood, and the redness of the blood is derived from the Fire of the Heart. In essence, blood is the Water of Tian Yi (One from Heaven), (as evidenced by its salty taste), and Qi is the Yang within Kan (Water trigram), sharing the same root in the Kidneys without divergence. Qi is rooted in the Kidneys and returns to the Kidneys; hence, it is said that the Kidneys receive Qi, resulting in deep breathing. (If Qi does not return to its origin, wheezing, coughing, and inability to lie flat occur.) The Lungs govern respiration, controlling the entry and exit of Qi. Furthermore, Qi ascends until it reaches the Lungs, where ascent reaches its peak and then descends; thus, the Lungs are said to be the masters of Qi. The Kidneys govern receiving Qi, so the Dantian (Elixir Field) is the Lower Sea of Qi; the Lungs govern Qi, so the chest is the Upper Sea of Qi. Kidney Water is steamed by the Yang within Kan, transforming into Qi, which rises to the Lungs. This is what is meant by "Essence transforms into Qi," analogous to earth qi rising to become clouds. Qi returns to the Lungs and transforms back into water; the Lungs distribute water essence, transporting it downward to the Bladder, circulating through the five meridians. (The essence of water travels through the meridians.) This is what is meant by "Water issues from high sources, heaven qi descends to become rain." The mutual rooting of Yin and Yang can be understood here. The Kidneys function by storing and consolidating. Although Yang arises at Zi hour (11 PM–1 AM) from the abyssal spring, the mechanism is not yet fully unblocked; therefore, the ascending and developing nature of Qi belongs to the Liver rather than the Kidneys. Storage belongs to the Kidneys, while discharge/ascending belongs to the Liver (Ascending is a form of discharge); this distinguishes the Liver and Kidneys. The Liver governs ascending, and the Lungs govern descending; this distinguishes the Lungs and Liver. The Heart governs movement, (when will is unified, it moves Qi), and the Kidneys govern stillness; this distinguishes the Heart and Kidneys. Stillness prevents desiccation, movement prevents exhaustion, ascending prevents floating, and descending prevents sinking; these functions belong to the Spleen, governed by the virtue of Harmony and Centrality. Therefore, if ascending/descending and movement/stillness lose their balance, even if the Liver, Lungs, Heart, and Kidneys fail in their duties, it is ultimately the failure of the Spleen. To know only that Qi fails to ascend, or ascends without descending, attributing it to Liver Wood overacting on Spleen Earth, is narrow-minded. To know that diseases of all organs relate to the Spleen is to know that harmonizing Spleen Qi harmonizes all organs. Thus, saying "tonifying the Spleen is inferior to tonifying the Kidneys" is merely a summary statement; therefore, the argument that "tonifying the Kidneys is inferior to tonifying the Spleen" is more comprehensive. For the elderly and children, the Spleen and Stomach are particularly paramount. *Jing* names Yang Qi after the swift winds of heaven and earth. It also states that Wind Qi communicates with the Liver; therefore, Qi disorders are often termed Wind, such as Liver Wind, Intestinal Wind, and Stomach Wind. (When food is in the Stomach, the Stomach is full and the Intestines empty, causing Qi to descend to the Intestines; when food is in the Intestines, the Intestines are full and the Stomach empty, causing Qi to ascend to the Stomach. The reciprocal stirring produces sound, which constitutes Intestinal Wind and Stomach Wind.) These are merely the reciprocating stirring of Qi resembling wind, not necessarily exogenous Wind pathogen. The above clarifies the principles of Qi; regarding pathological syndromes, pulse diagnosis, and treatment, see below.