马云。内有司内揣外。故名篇。说文云。揣、量也。六书统云。凡称量忖度。皆曰揣。
授其调 张云。调、法度也。言颇得其详也。
夫九针者（止）可乎 张云。始于一。终于九者。尽天地
之大数也。针数应之。故小则无内。大则无外。深则无下。高则无上。其于天道人事。四时之变。无所不合。
故散之则杂如毫毛。约之则浑束为一。一者欲得其要也。
夫治国者（止）为一乎 张云。至大至小。至浅至深。无不有道存焉。故治国者有道。治针亦有道。
必知乎道。乃可万变而为一矣。
动摇则应知 张云。有动则有应。有应则可知。惟其至明。故能尽得其情。
合而察之 切而验之 见而得之 马云。合阴阳而察之。切阴阳而验之。见阴阳而得之。张云。
合而察之。参合阴阳而详察也。切而验之。从其切要而辨证也。故可见可得。如清水明镜之无所失也。
五音不彰（止）影之似形 张云。五音五色见于外。因藏气而彰明也。五脏之气藏于内。因形声而发
露也。外之不彰不明者。知内之波荡也。即如鼓非桴也。得桴而后鸣响。非声也。得声而后应影。非形也。得
形而后见。是皆内外相袭而然。袭、因也。马云。五脏在人身者如水波。荡然紊乱无纪。
故远者（止）弗敢使泄也 张云。揣、推测也。司、主也。远者主外。近者主内。察其远能知其近。
察其内能知其外。病变虽多。莫能蔽吾之明矣。内外远近。无所不知。以其明之至也。阴阳之道。尽于此矣。
天地虽大。又安能出于是哉。马云。人身之音与色。是之谓远可以言外也。而即外可以揣五脏之在内者。人身
之五脏。是之谓近可以言内也。而即内可以揣音与色之在外者。此乃阴阳之极。天地之秘。盖不可以轻泄之乎。
刺节真邪论。及素问灵兰秘典论。皆藏此室。简案、司、伺通。汉灌夫。传外后亦已使侯司。
马云说：“内有司内揣外”，因此以“外揣”命名本篇。《说文解字》说：揣，是量度的意思。《六书统》说：凡是称量、忖度，都称为揣。
“授其调”：张景岳说：调，指法度。意思是论述颇为详尽。
“夫九针者（止）可乎”：张景岳说：始于一，终于九，是穷尽天地的最大数。针的数量与之相应，所以小则无内（极小），大则无外（极大），深则无下（极深），高则无上（极高）。它对于天道人事、四时的变化，没有不相合的。
所以散开来看则杂乱如毫毛，归纳起来则浑厚统一为一。“一”就是要掌握其要领。
“夫治国者（止）为一乎”：张景岳说：无论至大至小，至浅至深，无不有道存在于其中。所以治国有道，治针也有道。必须知晓这个道，才能应对万变而归于一致。
“动摇则应知”：张景岳说：有动就有反应，有反应就可以知道。正因为极其明察，所以能完全了解病情。
“合而察之，切而验之，见而得之”：马云说：综合阴阳来观察它，切按阴阳来验证它，见到阴阳来获得诊断。张景岳说：合而察之，是参合阴阳而详细考察；切而验之，是从切要处进行辨证。所以可见可得，就像清水和明镜一样无所遗漏。
“五音不彰（止）影之似形”：张景岳说：五音五色显现于外，是因为脏腑之气而彰显明白。五脏之气藏于内，因为形体声音而显露出来。外部如果不彰显不明朗，就知道内部有波动激荡。这就好比鼓不是槌，得到槌后才鸣响；声不是影，得到声后才出现对应的影；形不是见，得到形后才能看见。这些都是内外相互因袭而产生的。袭，就是因的意思。马云说：五脏在人身中就像水波，荡荡然紊乱没有条理。
所以“远者（止）弗敢使泄也”：张景岳说：揣，是推测；司，是主掌。远者主外，近者主内。观察外在就能知道内在，观察内在就能知道外在。病变虽然多，但不能遮蔽我的明察。内外远近，无所不知，这是因为明察到了极点。阴阳的道理，全都在这里了。天地虽然广大，又怎能超出这个范围呢？马云说：人身上的声音与面色，这就叫作远，可以据此推论外在表现；而即从外在表现可以推测五脏在体内的状况。人身的五脏，这就叫作近，可以据此推论内在；而即从内在可以推测声音与面色在外在的表现。这是阴阳的极致，天地的秘密，大概不可以轻易泄露吧。
《刺节真邪论》及《素问·灵兰秘典论》，都收藏在这个道理之中。简案：司、伺相通。汉代灌夫的传记中提到“外后亦已使侯司”。
Ma Yun states: "The internal governs the external through estimation," hence the chapter is named "Wai Chuai" (Estimating from the Exterior). The *Shuowen Jiezi* explains: "Chuai" means to measure or estimate. The *Liushu Tong* states: All acts of weighing and deliberating are termed "Chuai."
Regarding "Shou Qi Diao" (Imparting its regulation): Zhang Jingyue explains that "Diao" refers to laws or standards, indicating that the discourse is quite detailed.
Regarding "Fu Jiu Zhen Zhe... Ke Hu" (As for the nine needles... is it permissible?): Zhang Jingyue explains that beginning with one and ending with nine exhausts the great numbers of heaven and earth. The number of needles corresponds to this; thus, they are small without interior limit, large without exterior limit, deep without lower limit, and high without upper limit. They align perfectly with the Way of Heaven and human affairs, as well as the changes of the four seasons.
Therefore, when scattered, they appear as chaotic as hairs; when condensed, they are unified into one. "One" implies grasping the essential principle.
Regarding "Fu Zhi Guo Zhe... Wei Yi Hu" (Does governing a state... amount to unity?): Zhang Jingyue explains that whether vast or minute, shallow or deep, the Way exists in all things. Thus, there is a Way to govern a state, and a Way to use needles. One must understand this Way to transform myriad changes into unity.
Regarding "Dong Yao Ze Ying Zhi" (Movement elicits response, which can be known): Zhang Jingyue explains that where there is movement, there is a response; where there is a response, it can be known. Only through utmost clarity can one fully comprehend the condition.
Regarding "He Er Cha Zhi, Qie Er Yan Zhi, Jian Er De Zhi" (Synthesize to observe, palpate to verify, perceive to obtain): Ma Yun states: Synthesize Yin and Yang to observe them; palpate Yin and Yang to verify them; perceive Yin and Yang to obtain the diagnosis. Zhang Jingyue elaborates: "He er cha zhi" means to synthesize Yin and Yang for detailed observation; "Qie er yan zhi" means to differentiate syndromes based on key palpable signs. Thus, what is visible and obtainable is like clear water or a bright mirror, losing nothing.
Regarding "Wu Yin Bu Zhang... Ying Zhi Si Xing" (Five tones not manifesting... shadow resembling form): Zhang Jingyue explains: Five tones and five colors manifest externally due to the Qi of the Zang organs becoming apparent. The Qi of the five Zang organs is stored internally but revealed through physical form and sound. If the exterior does not manifest clearly, it indicates internal turbulence. This is like a drum not being the mallet; only with the mallet does it resonate. Sound is not the shadow; only with sound does the corresponding shadow appear. Form is not perception; only with form is it seen. These are all results of internal and external mutual causation ("Xi" means causation/dependence). Ma Yun adds: The five Zang organs within the body are like waves, turbulent and disordered.
Therefore, regarding "Yuan Zhe... Fu Gan Shi Xie Ye" (The distant... dare not be leaked): Zhang Jingyue explains: "Chuai" is speculation; "Si" is governance/control. The distant governs the exterior, the proximate governs the interior. Observing the distant allows knowing the proximate; observing the interior allows knowing the exterior. Although diseases vary, none can obscure my clarity. Knowing both interior/exterior and distant/proximate stems from utmost clarity. The Way of Yin and Yang is fully contained herein. Though heaven and earth are vast, how could they exceed this? Ma Yun states: The sounds and colors of the body represent the "distant," allowing inference of external manifestations; from these externals, one estimates the internal five Zang organs. The five Zang organs represent the "proximate," allowing inference of the internal; from the internal, one estimates the sounds and colors manifested externally. This is the extreme of Yin and Yang, the secret of heaven and earth, which should not be lightly disclosed.
These principles are also found in the *Ci Jie Zhen Xie Lun* and the *Ling Lan Mi Dian Lun*. Note: "Si" and "Si" (to watch/govern) are interchangeable. In the biography of Guan Fu of the Han Dynasty, it mentions "the outer post had already appointed Hou Si."