三焦下 ，在于足大指之前，少阳之后，出于 中外廉，名曰委阳。足太阳络也，手少阳经也。
〔《铜人》〕云∶委阳，在足太阳之前，少阳之后，出于 中外廉两筋间，承扶下六寸，此足太阳之别络。
刺入七分，留五呼，灸三壮，屈身而得之。详《铜人》云∶委阳在承扶下六寸，以今经文考之，当云一尺六寸。
谨按经文论委阳，在足太阳之前，少阳之后，出于 中外廉。又按经文取合穴法，取委阳者屈伸而索之，
取阳陵泉者正竖膝与之齐，下至委阳之前取之，是知委者曲也。委中即两 之中央，委阳即曲 之阳分，约文之
尽处，两筋间是。推其分野，正当太阳少阳之间，内外廉之界，故曰太阳之前，少阳之后， 中外廉也。
其穴正在约文尽处，两筋之间，屈伸而得之，故取法曰屈伸索之也。只正膝与之齐，阳陵泉正对其
穴，故曰取阳陵泉者，下至委阳之前取之也。又考诸尺寸则承扶下至其穴，正得一尺六寸，故愚断然谓《甲乙》
脱去“一尺”二字，无疑也。
三焦者，足少阳太阳之所将，太阳之别也。上踝五寸，别入贯 肠，出于委阳，并太阳之正，入络膀胱，
三焦的下合穴，位于足大趾之前、少阳经之后，出于小腿后外侧两筋之间，名为委阳。它是足太阳膀胱经的络脉，也是手少阳三焦经的下合穴。
《铜人腧穴针灸图经》记载：委阳穴，在足太阳经之前、少阳经之后，出于小腿后外侧两筋之间，在承扶穴下方六寸处，这是足太阳膀胱经的别络。
针刺深度为七分，留针时间为五次呼吸的时间，艾灸三壮，取穴时需屈身才能找到。详细查阅《铜人腧穴针灸图经》说：委阳在承扶穴下六寸，但根据本文经文考证，应当说是十六寸。
谨按经文论述委阳穴，位于足太阳经之前、少阳经之后，出于小腿后外侧两筋之间。又按照经文选取下合穴的方法，选取委阳穴时，需通过屈伸腿部来寻找；选取阳陵泉穴时，需正坐竖膝使其与穴位齐平，向下至委阳穴前方取穴，由此可知“委”字意为弯曲。委中穴即腘窝横纹中央，委阳穴即弯曲腘窝处的阳分一侧，也就是文字描述的尽头处，即两筋之间。推究其部位分野，正当处于太阳经和少阳经之间，内外侧边缘的交界处，所以说是在太阳经之前、少阳经之后，即小腿后外侧两筋之间。该穴正好位于腘窝横纹尽头处、两筋之间，通过屈伸动作即可找到，所以取穴方法称为“屈伸而索之”。只要正坐竖膝使其与穴位齐平，阳陵泉穴正好对着该穴，所以说选取阳陵泉穴时，是向下至委阳穴前方取穴。又考证各部位的尺寸，从承扶穴下到该穴，正好是一尺六寸，所以我断然认为《甲乙经》脱去了“一尺”二字，毫无疑问。
三焦经，是由足少阳胆经和足太阳膀胱经所统摄，属于足太阳膀胱经的别络。在上踝骨上方五寸处，别行进入并贯穿大肠，出于委阳穴，并与足太阳膀胱经的正脉并行，进入并联络膀胱。
The lower He-Sea point of the Sanjiao (Triple Burner) is located anterior to the big toe and posterior to the Shaoyang channel, emerging between the medial and lateral tendons of the lower leg. It is named Weiyang (BL39). It is the connecting vessel of the Foot-Taiyang Bladder Channel and the lower He-Sea point of the Hand-Shaoyang Sanjiao Channel.
According to *Tongren* (Illustrated Manual of Acupoints), Weiyang is located anterior to the Foot-Taiyang channel and posterior to the Shaoyang channel, emerging between the two tendons on the lateral aspect of the lower leg, six cun below Chengfu (BL36). This is the divergent vessel of the Foot-Taiyang Bladder Channel.
Needle insertion depth is 7 fen; retain the needle for five breaths; moxibustion consists of three cones. The point is accessed by flexing the body. Detailed examination of *Tongren* states that Weiyang is six cun below Chengfu; however, based on a textual analysis of this classic, it should be stated as sixteen cun.
Respectfully consulting the classic text regarding Weiyang: it is located anterior to the Foot-Taiyang channel and posterior to the Shaoyang channel, emerging between the medial and lateral tendons. Furthermore, according to the method for locating He-Sea points described in the classics: when locating Weiyang, one seeks it through flexion and extension of the limb; when locating Yanglingquan (GB34), one sits upright with the knee vertical and level with the point, seeking it forward from Weiyang. From this, we know that "Wei" (委) implies bending or flexion. Weizhong (BL40) is at the center of the popliteal crease; Weiyang is on the Yang (lateral/posterior) side of the flexed popliteal region, specifically at the end of the descriptive boundary, which is between the two tendons. Analyzing its anatomical territory, it lies precisely between the Taiyang and Shaoyang channels, at the boundary of the medial and lateral aspects, hence described as anterior to Taiyang and posterior to Shaoyang, i.e., between the medial and lateral tendons. The point is exactly at the end of the popliteal crease, between the two tendons, accessible through flexion and extension; thus, the retrieval method is described as "seek through flexion and extension." If sitting upright with the knee vertical, Yanglingquan aligns directly with this point; therefore, the instruction "locate Yanglingquan... seek forward to Weiyang" refers to this alignment. Further dimensional verification confirms that the distance from Chengfu to this point is exactly one chi and six cun. Therefore, I firmly conclude that the *Jia Yi Jing* (Systematic Classic of Acupuncture and Moxibustion) omitted the characters "one chi," without doubt.
The Sanjiao channel is governed by the Foot-Shaoyang Gallbladder Channel and the Foot-Taiyang Bladder Channel; it is a divergent branch of the Foot-Taiyang Bladder Channel. Five cun above the malleolus, it branches off, passes through the intestines, emerges at Weiyang (BL39), runs parallel with the main trunk of the Foot-Taiyang Bladder Channel, enters and connects with the Bladder.