按李时珍云。命门为藏精系胞之物。其体非脂非肉。白膜裹之。在脊骨第七节两肾中。
此火
下通二肾。上通心肺。贯脑。为生命之源。相火之主。精气之府。人物皆有。生人生物。俱
由此出。又按汪昂谓。人无此火。则神机灭息。生气消亡。赵养葵谓。火可以水折。惟水中
之火不可以水折。故必择其同气招引归宇。则火始不上浮而下降矣！此火之所由补也。第
世止知附桂为补火之最。硫黄为火之精。越外毫不计及。更不知其附桂因何相需必用。讵知
火衰气寒而厥。则必用以附子。火衰血寒腹痛。则必用以肉桂。火衰寒结不解。则必用以硫
黄。火衰冷痹精遗。则必用以仙茅。火衰疝瘕偏坠。则必用以胡巴。火衰气逆不归。则必用
以沉香。火衰肾泄不固。则必用以补骨脂。火衰阳痿血瘀。则必用以阳起石。火衰风冷麻痹
。则必用以淫羊藿。火衰风湿疮痒。则必用以蛇床子。火衰脏寒蛊生。则必用以川椒。火衰
气逆呃起。则必用以丁香。火衰精涎不摄。则必用以益智。至于阳不通督。须用鹿茸以补之
。火不交心。须用远志以通之。水窍不开。须用钟乳石以利之。气虚喘乏。须用蛤蚧以御之
。精滑不禁。须用阿芙蓉以涩之。皆当随症酌与。不可概用。若使水火并衰。及或气陷不固
。阴精独脱。尤当切禁。否则祸人反掌。
据李时珍所说，命门是藏精和系胞的器官。它的形体既不是脂肪也不是肌肉，而是由白膜包裹着，位于脊柱第七节两侧肾脏之中。
这火（命门之火）向下通达两肾，向上通达心肺，贯通脑部，是生命的源头，相火的主宰，精气汇聚之所。人和动物都有它，生育人类、化生万物，都由此而出。
又据汪昂所说，人如果没有这火，那么神机就会熄灭，生气就会消亡。赵养葵说，火可以被水克制，只有水中的火不可以被水克制。所以必须选择与它同类的气来招引，使其回归本位，这样火才不会上浮而下降！这就是补益这火的缘由。
只是世人只知道附子、肉桂是补火的最佳药物，硫黄是火的精华，却完全不顾及其他方面，更不知道它们为何必须相互配合使用。岂不知：
火衰导致气寒而发生厥逆，则必须使用附子；
火衰导致血寒引起腹痛，则必须使用肉桂；
火衰导致寒邪凝结不解，则必须使用硫黄；
火衰导致冷痹和遗精，则必须使用仙茅；
火衰导致疝气和偏坠，则必须使用胡巴（小茴香）；
火衰导致气逆不降，则必须使用沉香；
火衰导致肾虚泄泻且固摄无力，则必须使用补骨脂；
火衰导致阳痿和血瘀，则必须使用阳起石；
火衰导致风冷麻痹，则必须使用淫羊藿；
火衰导致风湿疮痒，则必须使用蛇床子；
火衰导致脏腑寒冷而生蛊毒，则必须使用川椒；
火衰导致气逆呃逆发作，则必须使用丁香；
火衰导致精液和涎沫不能摄持，则必须使用益智仁。
至于阳气不通督脉，须用鹿茸来补益；
火不与心相交，须用远志来交通；
水窍不开，须用钟乳石来通利；
气虚喘息乏力，须用蛤蚧来抵御；
精滑不禁，须用阿芙蓉来涩止。
这些都应当根据症状斟酌给予，不可一概使用。如果水火俱衰，以及气陷不固、阴精独脱的情况，尤其应当严格禁忌。否则祸害人的速度就在转掌之间。
According to Li Shizhen, the Mingmen (Gate of Life) is an organ that stores essence and connects to the uterus. Its substance is neither fat nor flesh, but is wrapped in a white membrane, located between the two kidneys at the seventh vertebral level of the spine.
This Fire (Fire of the Gate of Life) extends downward to connect with the two kidneys, upward to connect with the Heart and Lungs, and penetrates the brain. It is the source of life, the master of Ministerial Fire (Xiang Huo), and the repository of essence and Qi. Both humans and animals possess it; the generation of humans and the creation of all things all originate from here.
Furthermore, according to Wang Ang, if a person lacks this Fire, their Shen (Spirit) mechanisms will cease, and their vital Qi will perish. Zhao Yangkui stated that while ordinary Fire can be subdued by Water, the Fire within Water cannot be subdued by Water. Therefore, one must select substances with similar properties to attract and guide it back to its origin, so that the Fire will no longer float upward but descend properly. This is the rationale for tonifying this Fire.
However, people of the world only know that Fuzi (Prepared Aconite Root) and Rougui (Cinnamon Bark) are the best herbs for tonifying Fire, and Huhuang (Sulfur) is the essence of Fire, completely neglecting other aspects, and further failing to understand why these specific herbs must be used in conjunction.
Consider this:
When Fire deficiency leads to Cold Qi and Jue syndrome (cold extremities/loss of consciousness), Fuzi (Prepared Aconite Root) must be used.
When Fire deficiency leads to Blood Cold causing abdominal pain, Rougui (Cinnamon Bark) must be used.
When Fire deficiency leads to unresolved Cold coagulation, Huhuang (Sulfur) must be used.
When Fire deficiency leads to Cold Bi syndrome (painful obstruction) and spermatorrhea, Xianmao (Curculigo Rhizome) must be used.
When Fire deficiency leads to Hernia (Shan Jia) and testicular retraction/pain, Huba (Fennel Fruit/Xiao Hui Xiang) must be used.
When Fire deficiency leads to rebellious Qi failing to descend, Chenxiang (Agarwood) must be used.
When Fire deficiency leads to Kidney-type diarrhea without retention control, Buguzhi (Psoralea Fruit) must be used.
When Fire deficiency leads to Impotence and Blood stasis, Yangqishi (Calcined Pyrolusite) must be used.
When Fire deficiency leads to Wind-Cold numbness and paralysis, Yinyanghuo (Epimedium Herba) must be used.
When Fire deficiency leads to Wind-Damp skin sores and itching, Chuangzi (Cnidium Fruit) must be used.
When Fire deficiency leads to Internal Cold and Gu poison (parasitic disease), Chuanjiao (Sichuan Pepper) must be used.
When Fire deficiency leads to rebellious Qi and hiccups, Dingxiang (Clove) must be used.
When Fire deficiency fails to secure Essence and saliva, Yizhi (Alpinia Oxyphylla Fruit) must be used.
Regarding cases where Yang Qi does not unblock the Du Meridian, Lurong (Deer Antler Velvet) must be used to tonify it.
Where Fire does not interact with the Heart, Yuanzhi (Polygala Root) must be used to facilitate communication.
Where the water orifices are not open, Zhongrushí (Stalactite) must be used to promote drainage.
Where Qi deficiency causes panting and fatigue, Gejie (Gekko Gecko) must be used to manage it.
Where Essence slips uncontrollably, Afuyou (Opium) must be used to astringe it.
All of these should be administered according to careful consideration of symptoms and must not be used indiscriminately. If both Water and Fire are deficient, or if there is sinking Qi without retention, or solitary collapse of Yin Essence, such conditions are strictly contraindicated. Otherwise, the harm inflicted upon the patient will occur in the blink of an eye.