（《灵枢·邪客篇》）
黄帝问于岐伯曰∶人有八虚，各何以候？（八虚，即《五脏生成篇》所谓八溪也，是皆筋骨之隙，气血之所流注者，
故曰八虚。）岐伯答曰∶以候五脏。（谓可因八虚以察五脏之病。）黄帝曰∶候之奈何？岐伯曰∶肺心有邪，其气留于两肘。
（人之五脏，惟肺与心居于膈上，其经属手，脾肝肾俱在膈下，其经属足，故肺心有邪，乘虚而聚，其气必留于两肘，
在肺则尺泽，在心则少海之次。）肝有邪，其气流于两腋。（肝与胆合，其经自足而上，皆行胁腋之间，故肝邪乘虚而聚
者，其气当流于两腋，即期门、渊腋等穴之次。）脾有邪，其气留于两髀。（脾与胃合，其脉皆自胫股上出冲门、气冲之
间，故邪气留于髀跨间者，知为脾经之病。髀，并米切，又音比。）肾有邪，其气留于两 。（肾与膀胱为表里，其经皆
出膝后阴谷、委中之间，故邪气留于两 者，知为肾经之病。 音国。）凡此八虚者，皆机关之室，真气之所过，血络之
所游，邪气恶血固不得住留，住留则伤经络骨节机关，不得屈伸，故 挛也。（机，枢机也。关，要会处也。室，犹房室
也。凡此八者，皆气血之所由行也，正气居之则为用，邪气居之则伤经络机关，而屈伸为之不利，此八虚可候五脏也。
音拘。）
（出自《灵枢·邪客篇》）
黄帝向岐伯问道：人体有八个虚损部位，分别用来诊察什么？（所谓的“八虚”，就是《五脏生成篇》中提到的“八溪”，这些都是筋骨之间的缝隙，是气血流注的地方，所以称为“八虚”。）
岐伯回答说：用来诊察五脏。（意思是可以通过观察这八个虚损部位来检查五脏的疾病。）
黄帝问：如何诊察呢？
岐伯说：肺和心如果有邪气，其病气会停留在两肘部。（人的五脏中，只有肺和心位于膈肌之上，它们的经脉属于手部；脾、肝、肾都在膈肌之下，它们的经脉属于足部。所以肺和心的邪气，会趁着虚弱之处聚集，病气必然停留在两肘部，在肺经则是尺泽穴附近，在心经则是少海穴附近。）
肝脏如果有邪气，其病气会流动于两腋部。（肝与胆相表里，它们的经脉从足部向上行走，都经过胁肋和腋窝之间，所以肝的邪气趁着虚弱之处聚集，病气应当流动于两腋部，即期门穴、渊腋穴等穴位附近。）
脾脏如果有邪气，其病气会停留在两髀部（大腿根部/腹股沟区域）。（脾与胃相表里，它们的脉气都从小腿和大腿向上出于冲门穴、气冲穴之间，所以邪气停留在髀跨间，可以知道是脾经的疾病。“髀”字读音为bǐ，又读作bì。）
肾脏如果有邪气，其病气会停留在两腘部（膝盖后方腘窝）。（肾与膀胱相表里，它们的经脉都出于膝后阴谷穴、委中穴之间，所以邪气停留在两腘部，可以知道是肾经的疾病。“腘”字读音为guó。）
大凡这八个虚损部位，都是关节活动的关键所在，是真气经过的地方，也是血络游行的场所。邪气和恶血本来不能在此停留，如果停留了，就会损伤经络、骨节和机关，导致肢体不能屈伸，因此会出现拘挛的症状。（“机”指枢机，“关”指要害交会之处，“室”如同房室一样。这八个部位，都是气血通行的地方，正气占据它们则发挥功能，邪气占据它们则损伤经络机关，导致屈伸不利，这就是为什么可以通过这八个虚损部位来诊察五脏疾病的原因。“拘挛”的“拘”字读音为jū。）
(From *Ling Shu: Evil Guest Chapter*)
The Yellow Emperor asked Qibo: The human body has eight "deficient" (Xu) areas. How can each be used for diagnosis? (The so-called "eight Xu" refers to the "eight streams" mentioned in the *Chapter on the Generation of the Five Zang Organs*. These are all gaps between sinews and bones, where Qi and Blood flow and pour through; hence they are called the "eight Xu".)
Qibo replied: They are used to diagnose the Five Zang organs. (This means that diseases of the Five Zang organs can be observed through these eight deficient areas.)
The Yellow Emperor asked: How is this diagnosis performed?
Qibo said: When there is evil Qi in the Lung and Heart, its pathogenic Qi remains in the two elbows. (Among the five Zang organs, only the Lung and Heart are located above the diaphragm, and their meridians belong to the hand; the Spleen, Liver, and Kidney are below the diaphragm, and their meridians belong to the foot. Therefore, when evil Qi affects the Lung and Heart, it gathers in the deficient areas, and its pathogenic Qi must remain in the two elbows. In the Lung meridian, this corresponds to the vicinity of Chize [LU-5]; in the Heart meridian, it corresponds to the vicinity of Shaohai [HT-3].)
When there is evil Qi in the Liver, its pathogenic Qi flows into the two axillae. (The Liver and Gallbladder are interior-exteriorly related. Their meridians ascend from the foot, passing through the hypochondrium and axilla regions. Thus, when Liver evil Qi gathers in the deficient areas, its pathogenic Qi flows into the two axillae, corresponding to the vicinity of acupoints such as Qimen [LR-14] and Yuanxi [GB-9].)
When there is evil Qi in the Spleen, its pathogenic Qi remains in the two thighs/groin areas (Bi). (The Spleen and Stomach are interior-exteriorly related. Their pulse Qi ascends from the lower leg and thigh, emerging between the Chongmen [SP-12] and Qichong [ST-30] regions. Therefore, if evil Qi remains in the groin/thigh area, it indicates a disease of the Spleen meridian. "Bi" is pronounced bǐ, or alternatively bì.)
When there is evil Qi in the Kidney, its pathogenic Qi remains in the two popliteal fossae (Guo). (The Kidney and Bladder are interior-exteriorly related. Their meridians emerge between the Yinvalley [BL-39] and Weizhong [BL-40] points behind the knee. Therefore, if evil Qi remains in the two popliteal fossae, it indicates a disease of the Kidney meridian. "Guo" is pronounced guó.)
Generally speaking, these eight deficient areas are chambers of joint mechanisms, places where True Qi passes, and routes where blood collaterals travel. Evil Qi and foul blood cannot naturally reside here. If they do reside, they damage the meridians, bones, joints, and mechanisms, leading to an inability to flex and extend, resulting in spasms or contractures. ("Ji" refers to the pivot/mechanism; "Guan" refers to key intersections; "Shi" is like a room. These eight areas are where Qi and Blood circulate. When Righteous Qi occupies them, they function normally; when Evil Qi occupies them, it damages the meridians and mechanisms, causing difficulty in flexion and extension. This is why the eight Xu areas can be used to diagnose the Five Zang organs. "Ju" is pronounced jū.)