营卫即气血。而名之曰营卫者。气血以体言。营卫以用言。故必另详其义也。气血之变化。男精女经。气血之功用。
阴营阳卫各有区分。尤宜详辨。此全是生人之作用。若剖视死人。则不得也。
人受气于谷其清者为营。浊者为卫。营在脉中。卫在脉外营周不休。五十度而复大会。阴阳相贯。如环无端。卫气。
行于阴二十五度行。于阳二十五度。分为昼夜。太阳主外。太阴主内。各行二十五度。平旦阴尽而阳受气矣。
营者血也。卫者气也。血守于内。如兵家之安营。故曰营气。御于外。如兵家之护卫。故曰卫。上编言浊气归心为
血。此言清者为营。浊者为卫。非刺谬也。上编浊字。指阴汁言。以阳为清。则阴为浊矣。此篇清浊。以刚柔言阴气柔
和为清阳气刚悍为浊。故曰清者为营浊者为卫也。营在脉中。谓营血由心。之脉管散为众管达于上下又有回脉管复回于
心。总在皮膜肌肉之里。以为阳气之守也。卫在脉外谓卫气上输于肺走于脏腑外达皮毛以护卫营气为阴之外卫也。营周
不休者。谓营行脉中周于通。身将人身三停内外。分为五十度。一日一夜。营血周行五十度。而复返。于肺与卫气大会
西医谓心有左右两房。生血由左房出。有运血管由内达外。然后入回血管由外返内。复入于心。回血色紫。返心过肺管。
呼气出。则吹去紫色。紫色者。炭气也。紫色已去仍变赤血。而返于心。由右房入。又由左房出。循环不休。西医此说。
即内经营周不休五十度而复大会之实迹也。所谓阴阳相贯。如环无端也。卫气之行则分阴阳内外。太阳在外为阳。太阴
在内为阴昼则卫气行阳二十五度。夜则行阴二十五度。平旦行阴已尽。阳分受气。是卫气复于肺与营相会矣卫行于阳则
寤。卫行于阴。则寐。故难经言卫行五十度。复会于手太阴。而人之卧起。皆卫气出。入之验也。灵枢云。人经脉前后
上下左右周身。十六丈二尺为一度。人一呼脉行三寸。一吸脉行三寸。计昼夜一万三千五百息。脉行五十度也。西医将
脉管剖视。自谓详矣。而不能分出各经。又不能共计其长短。于回血合气之数皆无从。起算然则西医。安能如中国古法
之精哉。
营出中焦。卫气出于下焦。
上言人受谷气。清者为营。浊者为卫。似营卫皆出中焦矣。而此又别之曰。卫气出于下焦。则尤为探源之论。盖人
身只此先后两天。为生化之本。营血虽生于心而取汁则在中焦。故曰营出中焦。是后天之所生化也。卫气虽统于肺。周
于太阳皮毛之间。而其气之化源。则在脐下丹田气海之中。是先天之所生化也。卫出先天。督脉主之。营出后天。任脉
主之。任督相贯。营卫相循。如此其精微也。旧注不知。乃谓卫气出于下焦之下字。当作上字。则诚误矣。
心者血肺者气。血为营气为卫相随上下。谓之营卫。
营卫虽生于中下二焦。然营卫之行。则统于心肺周行上下也上既言之而兹又引难经此语。取其详明。不厌烦复也。
此篇前二节。出灵枢。后一节出难经。再参看十二官。男女天癸血气诸条。自能通贯。
营气和卫气就是气和血。之所以称为营卫，是因为气血是从形体（物质基础）的角度来说的，而营卫是从功能作用的角度来说的。因此必须另行详细阐述其含义。气血的变化，体现在男子的精液和女子的月经中；气血的功能作用，阴性的营气和阳性的卫气各有区分，尤其应当详细辨别。这完全是生命活动的表现，如果剖视死人，就无法看到了。
人从饮食谷物中受纳精气，其中清轻的部分成为营气，重浊的部分成为卫气。营气行于脉管之中，卫气行于脉管之外。营气周身循环运行不停息，每昼夜运行五十周次后再次与卫气在肺会合。阴阳之气相互贯通，像圆环一样没有端点。卫气，白天行于阳分二十五周次，夜晚行于阴分二十五周次，以此划分昼夜。太阳经主司体表外部，太阴经主司体内内部，各自运行二十五周次。黎明时分，阴气尽而阳气开始受气。
营气就是血，卫气就是气。血守持于体内，如同兵家安扎营地，所以称为营气；卫气护卫于体外，如同兵家护卫军队，所以称为卫气。上编章节中说“浊气归心化为血”，这里说“清者为营，浊者为卫”，并非矛盾。上编中的“浊”字，是指阴性的汁液而言，以阳为清，则阴为浊。本篇中的清浊，是从刚柔的角度来说的：阴气柔和为清，阳气刚悍为浊。所以说清者成为营气，浊者成为卫气。
营气行于脉中，是指营血由心脏进入脉管，分散为众多小脉管到达身体上下，又有回血管将血液回流至心脏，始终位于皮膜肌肉之内，作为阳气的守备。卫气行于脉外，是指卫气向上输送到肺，流走于脏腑之外，通达皮毛，以护卫营气，作为阴气的外在护卫。
营气周身循环不停息，是指营气在脉中环绕全身，将人身分为三停内外，共计五十周次。一日一夜，营血循环五十周次，然后返回肺部与卫气大会。西医认为心脏有左右两个心房，血液由左房生出，通过运血管由内达外，然后进入回血管由外返内，再回到心脏。回血管中的血色紫暗，返回心脏经过肺管时，呼出气体，吹去紫色。紫色的是碳气，紫色去除后仍变为赤色血液，再返回心脏，由右房进入，又由左房排出，循环不息。西医的这种说法，正是内经中“营周不休，五十度而复大会”的实际痕迹。这就是所谓的“阴阳相贯，如环无端”。
卫气的运行则分为阴阳内外。太阳经在外为阳，太阴经在内为阴。白天卫气行于阳分二十五周次，夜晚行于阴分二十五周次。黎明时行于阴分的次数已尽，阳分开始受气，这是卫气重新回到肺部与营气相会合。卫气行于阳分则清醒，卫气行于阴分则睡眠。所以《难经》说卫气运行五十周次后，重新会合于手太阴肺经，人的睡醒起居，都是卫气出入的验证。《灵枢》说，人体经脉前后上下左右周身，十六丈二尺为一周次。人一呼气脉气运行三寸，一吸气脉气运行三寸，计算昼夜一万三千五百次呼吸，脉气运行五十周次。西医将脉管剖视，自以为详细了，但不能分出各条经脉，也不能共计其长短，对于回血与合气的数量都无从算起。那么西医怎么能比得上中国古法的精妙呢？
营气出于中焦，卫气出于下焦。
上文说人受纳谷气，清者为营，浊者为卫，似乎营卫都出于中焦。但这里又分别说“卫气出于下焦”，这更是探究本源的理论。大概人身只有先天和后天这两条根本，是生化之源。营血虽然生于心，但取汁化生则在中焦，所以说营气出于中焦，这是后天所生化。卫气虽然统属于肺，周行于太阳经皮毛之间，但其气化生的源头，则在脐下丹田气海之中，这是先天所生化。卫气出自先天，由督脉主司；营气出自后天，由任脉主司。任脉与督脉相互贯通，营气与卫气相互循行，如此精微。旧注不了解这一点，竟然说卫气出于下焦的“下”字，应当作“上”字，这就错了。
心主血，肺主气。血成为营，气成为卫，相随上下运行，称为营卫。
营卫虽然生于中、下二焦，然而营卫的运行，则统属于心肺，周行于全身上下。上面已经讲过，这里又引用《难经》的这句话，是为了取其详尽明确，不厌其烦复地讲解。本篇前两节内容出自《灵枢》，后一节内容出自《难经》，再参看关于十二官、男女天癸、血气等条目，自然能够融会贯通。
Ying (Nutrient) and Wei (Defensive) Qi are essentially Qi and Blood. They are named Ying and Wei because "Qi and Blood" refers to their substance (Ti), whereas "Ying and Wei" refers to their function (Yong). Therefore, their meanings must be detailed separately. The transformation of Qi and Blood is manifested in the essence of men and the menses of women. The functional roles of Yin Ying (Nutrient) and Yang Wei (Defensive) have distinct differences and should be carefully distinguished. This represents the vital functions of life; if one dissects a corpse, these cannot be observed.
Humans receive Qi from grain. The clear and light portion becomes Ying (Nutrient) Qi, while the turbid and heavy portion becomes Wei (Defensive) Qi. Ying Qi circulates within the vessels, while Wei Qi circulates outside the vessels. Ying Qi circulates ceaselessly throughout the body, completing fifty cycles per day and night before reuniting with Wei Qi at the lungs. Yin and Yang Qi interconnect continuously, like a circle without beginning or end. Wei Qi travels through the Yin aspects for twenty-five cycles during the night and through the Yang aspects for twenty-five cycles during the day, thereby distinguishing night from day. The Taiyang (Greater Yang) channel governs the exterior, while the Taiyin (Greater Yin) channel governs the interior; each performs twenty-five cycles. At dawn, when Yin Qi is exhausted, Yang Qi begins to receive its influence.
Ying Qi is Blood, and Wei Qi is Qi. Blood remains within the interior, akin to an army establishing a camp (Ying), hence it is called Ying Qi. Wei Qi guards the exterior, akin to an army providing protection (Wei), hence it is called Wei Qi. In the previous section, it was stated that "turbid Qi returns to the heart to become blood." Here, it states that "the clear becomes Ying and the turbid becomes Wei." This is not contradictory. The term "turbid" in the previous section referred to Yin fluids; regarding Yang as clear implies Yin is turbid. In this chapter, "clear" and "turbid" refer to softness and rigidity: Yin Qi is gentle and soft, thus considered clear; Yang Qi is vigorous and rigid, thus considered turbid. Hence, the clear becomes Ying Qi and the turbid becomes Wei Qi.
Saying "Ying Qi is within the vessels" means that Ying Blood flows from the heart into the vessels, disperses into numerous smaller vessels reaching the upper and lower parts of the body, and then returns to the heart via venous return vessels. It always resides within the fascia and muscles, serving as the guard for Yang Qi. Saying "Wei Qi is outside the vessels" means that Wei Qi ascends to the lungs, moves beyond the Zang-Fu organs, reaches the skin and hair, and protects Ying Qi, acting as the external defense for Yin.
"Ying Qi circulates ceaselessly" means that Ying Qi circulates through the entire body within the vessels. Dividing the human body into three sections internally and externally, it completes fifty cycles. In one day and night, Ying Blood circulates fifty times before returning to the lungs to meet with Wei Qi. Western medicine posits that the heart has left and right atria; blood is generated by the left atrium, travels outward via arteries, enters veins for return flow back to the heart. The blood in the veins appears purplish. Upon returning to the heart and passing through the pulmonary vessels, exhalation occurs, removing the purple hue. The purple color represents carbon dioxide gas. Once removed, the blood turns red again and returns to the heart, entering via the right atrium and exiting via the left atrium, circulating endlessly. This Western medical theory corresponds precisely to the actual physiological process described in the *Neijing* as "Ying Qi circulates ceaselessly, completing fifty cycles and reuniting." This is what is meant by "Yin and Yang Qi interconnect continuously, like a circle without beginning or end."
The movement of Wei Qi is divided into Yin/Yang and Interior/Exterior. The Taiyang channel is external and Yang; the Taiyin channel is internal and Yin. During the day, Wei Qi travels through the Yang aspects for twenty-five cycles; at night, it travels through the Yin aspects for twenty-five cycles. At dawn, having completed its journey through Yin, it receives Qi in the Yang aspect. This signifies that Wei Qi returns to the lungs to reunite with Ying Qi. When Wei Qi travels through Yang, one is awake; when it travels through Yin, one sleeps. Thus, the *Nanjing* states that after traveling fifty cycles, Wei Qi reunites with the Hand-Taiyin Lung Meridian. Human sleep and wakefulness are verifications of the entry and exit of Wei Qi. The *Lingshu* states that the meridians of the human body, front, back, up, down, left, and right, measure sixteen zhang and two chi for one cycle. With each exhalation, pulse Qi moves three cun; with each inhalation, it moves three cun. Calculating over twenty-four hours, there are thirteen thousand five hundred breaths, during which pulse Qi completes fifty cycles. Western medicine dissects blood vessels and claims thoroughness, yet they cannot distinguish individual meridians nor calculate their total length. Regarding the numbers of venous return and Qi integration, they have no basis for calculation. How can Western medicine compare to the precision of ancient Chinese methods?
Ying Qi originates from the Middle Jiao, while Wei Qi originates from the Lower Jiao.
Previously, it was said that humans receive Grain Qi, where the clear becomes Ying and the turbid becomes Wei, implying both originate from the Middle Jiao. However, here it distinguishes them by stating "Wei Qi originates from the Lower Jiao," which is a deeper exploration of origins. Essentially, the human body relies on only two roots—Pre-Heaven (Congenital) and Post-Heaven (Acquired)—as the source of generation and transformation. Although Ying Blood is generated by the Heart, its fluid extraction occurs in the Middle Jiao; therefore, it is said that "Ying Qi originates from the Middle Jiao," representing Post-Heaven generation. Although Wei Qi is governed by the Lungs and circulates among the Taiyang channels and skin/hair, its source of Qi transformation lies in the Dantian and Qihai below the navel, representing Pre-Heaven generation. Wei Qi emerges from Pre-Heaven and is governed by the Du Mai (Governing Vessel); Ying Qi emerges from Post-Heaven and is governed by the Ren Mai (Conception Vessel). The Ren and Du vessels interconnect, and Ying and Wei Qi circulate mutually, demonstrating such subtlety. Old commentaries failed to understand this, erroneously suggesting that the character "Lower" (Xia) in "Wei Qi originates from the Lower Jiao" should be read as "Upper" (Shang). This is indeed incorrect.
The Heart governs Blood, and the Lungs govern Qi. Blood becomes Ying, and Qi becomes Wei; following each other up and down, they are called Ying and Wei.
Although Ying and Wei are generated in the Middle and Lower Jiao, their circulation is governed by the Heart and Lungs, circulating throughout the upper and lower body. As mentioned above, this passage cites the *Nanjing* for clarity and detail, repeating the explanation without tiring of redundancy. The first two sections of this chapter are derived from the *Lingshu*, and the final section is derived from the *Nanjing*. By cross-referencing entries on the Twelve Officials, Tian Gui (Heavenly Water/Menstrual Essence) in men and women, and Qi and Blood, one can achieve comprehensive understanding.