精藏于肾，人尽知之。至精何以生，何以藏，何以出？则人不知也。夫精，即肾中之脂
膏也
。有长存者，有日生者。肾中有藏精之处，充满不缺，如井中之水，日夜充盈，此长存者也
。其欲动交媾所出之精，及有病而滑脱之精，乃日生者也。其精施去施生，不去亦不生，犹
井中之水，日日汲之，不见其亏；终年不汲，不见其溢。《易》云∶井道不可不革，故受之
以革，其理然也。曰∶然则纵欲可无害乎？曰∶是又不然。盖天下之理，总归自然。有肾气
盛者，多欲无伤；肾气衰者，自当节养。《左传》云∶女不可近乎？对曰∶节之。若纵欲不
节，如浅狭之井，汲之无度，则枯竭矣。曰∶然则强壮之人而绝欲，则何如？曰∶此亦无咎
无誉，惟肾气略坚实耳。但必浮火不动，阴阳相守则可耳。若浮火日动而强制之，则反有害
。盖精因火动而离其位，则必有头眩、目赤、身痒、腰疼、遗泄、偏坠等症，其者或发痈疽
，此强制之害也。故精之为物，欲动则生，不动则不生。能自然不动则有益，强制则有害，
过用则衰竭。任其自然，而无所勉强，则保精之法也。老子云∶无法道，道法自然，自然之
道，乃长生之诀也。
人之死，大约因元气存亡而决。故患病者，元气已伤，即变危殆。盖元气脱，则五脏六
腑皆
无气矣。竟有元气深固，其根不摇，而内中有一脏一腑先绝者。如心绝，则昏昧不知世事；
肝绝，则喜怒无节；肾绝，则阳道痿缩；脾绝，则食入不化；肺绝，则气促声哑。六腑之绝
，而失其所司亦然。其绝之象，亦必有显然可见之处。大约其气尚存，而神志精华不用事耳
，必明医乃能决之。又诸脏腑之中，惟肺绝则死期尤促。盖肺为脏腑之华盖，脏腑赖其气以
养，故此脏绝，则脏腑皆无禀受矣。其余则视其绝之甚与不甚，又观其别脏之盛衰何如，更
观其后天之饮食何如，以此定其吉凶，则修短之期可决矣。然大段亦无过一年者。此皆得之
目睹，非臆说也。
精液储藏于肾脏，这是人人都知道的。至于精液是如何生成的、如何储藏的、又是如何排出的，人们就不了解了。所谓精，就是肾中的脂膏。其中有长期存在的，也有每日新生的。肾脏中有储藏精液的地方，充满而不缺乏，就像井里的水一样，日夜充盈，这就是长期存在的精。而在性欲冲动进行交媾时排出的精，以及生病时滑脱流失的精，则是每日新生的。精液的排出与新生交替进行，不排出也不新生，就像井里的水，每天汲取它，看不出亏损；整年不汲取，也看不出溢出。《易经》说：井道不能不改革，所以接着用“革”卦来解释，道理就是这样。有人问：那么纵欲就没有害处吗？回答说：这又不对了。大概天下的道理，总归于自然。有肾气旺盛的人，多欲也无妨；肾气衰弱的人，自然应当节制保养。《左传》说：女子不可亲近吗？回答说：要有所节制。如果纵欲而不加节制，就像浅而窄的井，汲取没有限度，就会枯竭。有人问：那么身体强壮的人完全禁欲，怎么样呢？回答说：这也算无过也无功，只是肾气略微坚实罢了。但必须保证虚火不动，阴阳相互守持才可以。如果虚火每天妄动而强行抑制，反而会有害处。因为精液因火动而离开其正常位置，就必然会出现头晕、眼红、身痒、腰痛、遗精、睾丸偏坠等症状，有的人还会发生痈疽，这就是强行抑制的危害。所以精这种东西，欲望冲动时就生成，不冲动时就不生成。能够自然地不冲动就有好处，强行抑制就有危害，过度使用就会衰竭。顺应自然，而不勉强自己，这才是保精的方法。老子说：无法之法，道法自然，自然的法则，才是长生的秘诀。
人的死亡，大致由元气的存亡来决定。所以患病的人，元气已经受伤，病情就会变得危急。大概元气脱失，那么五脏六腑都没有气了。竟然有元气深固，根基不动摇，而内部有一脏或一腑先绝灭的情况。比如心绝，就会神志昏昧不知道世事；肝绝，就会喜怒没有节制；肾绝，就会性功能痿缩；脾绝，就会食物吃进去不消化；肺绝，就会气短声音嘶哑。六腑的绝灭，失去它们所主管的功能也是同样的情况。它们绝灭的迹象，也一定有明显可见的地方。大概此时气还存留，但神志精华不再起作用罢了，必须由明医才能判断。又在各个脏腑之中，只有肺绝则死期特别急促。因为肺是脏腑的华盖（保护伞），脏腑依赖肺的气来滋养，所以这个脏器绝灭，那么脏腑都没有禀受了。其余的则要看绝灭的程度严重还是不严重，又要观察其他脏器的盛衰如何，更要观察后天饮食的情况如何，根据这些来确定吉凶，那么寿命的长短就可以决定了。但大体上也没有超过一年的。这些都是亲眼目睹得到的，不是凭空臆说的。
Essence is stored in the Kidney, which everyone knows. However, how essence is generated, how it is stored, and how it is discharged, people do not understand. Essence is the fat and paste within the Kidney. There are those that exist for a long time, and those that are produced daily. Within the Kidney, there is a place where essence is stored, full and lacking nothing, like water in a well, filling up day and night; this is the long-lasting essence. The essence discharged during sexual desire and intercourse, as well as the essence lost through sliding and leakage due to illness, is the daily-produced essence. The discharge and generation of essence alternate; if not discharged, it is not generated, just like water in a well: drawing from it daily does not show a decrease, and not drawing from it for a whole year does not show an overflow. The *I Ching* (Book of Changes) states: "The way of the well cannot remain unchanged, therefore it is followed by Ge (Revolution)," which illustrates this principle. One might ask: Does this mean indulging in lust causes no harm? The answer is: This is incorrect. Generally, the principles of the world return to nature. Those with abundant Kidney Qi can indulge without injury; those with declining Kidney Qi should naturally practice moderation and nourishment. The *Zuo Zhuan* asks: "Should women not be approached?" The reply is: "One must exercise restraint." If one indulges in lust without restraint, it is like a shallow and narrow well: drawing from it without limit will lead to depletion. One might ask: What about a robust person who completely abstains from sex? The answer is: This results in neither merit nor fault, merely making the Kidney Qi slightly more solid. However, one must ensure that floating fire does not move and that Yin and Yang guard each other. If floating fire moves daily but is forcibly suppressed, it will cause harm. Because essence leaves its proper position due to fire movement, symptoms such as dizziness, red eyes, body itching, lower back pain, seminal emission, and unilateral testicular swelling or descent will inevitably occur; some may even develop carbuncles and ulcers. These are the harms of forced suppression. Therefore, essence is such that it is generated when desire stirs, and not generated when it does not stir. Natural non-stirring is beneficial; forced suppression is harmful; overuse leads to exhaustion. Following nature without forcing oneself is the method for preserving essence. Laozi said: "There is no fixed law; the Dao follows nature." The way of nature is the secret to longevity.
Human death is generally determined by the presence or absence of Yuan Qi (Original Qi). Thus, when a person falls ill, their Yuan Qi is already injured, making the condition critical. When Yuan Qi escapes, the Five Zang and Six Fu organs all lose their Qi. Yet, there are cases where Yuan Qi is deeply rooted and stable, while internally one Zang or one Fu organ fails first. For example, Heart failure leads to confusion and unawareness of worldly affairs; Liver failure leads to uncontrolled anger and joy; Kidney failure leads to impotence; Spleen failure leads to inability to digest food; Lung failure leads to shortness of breath and hoarseness. The failure of the Six Fu organs, losing their respective functions, is also the same. The signs of their failure must have obvious visible manifestations. Generally, Qi still exists, but the spirit, consciousness, and essence cease to function; only a skilled physician can determine this. Among all Zang and Fu organs, Lung failure leads to death most rapidly. Because the Lung is the canopy (Huagai) of the Zang and Fu organs, and they rely on its Qi for nourishment, when this organ fails, the Zang and Fu organs receive no endowment. For the others, prognosis depends on the severity of the failure, the strength or weakness of other organs, and the state of post-heaven dietary intake. Based on these, one can determine auspiciousness or inauspiciousness, and thus predict the length of life. However, generally, it does not exceed one year. These observations are based on personal experience, not speculation.