（此卫气所行也。卫行脉外）
人身头与手足是一壳子，五脏六腑皆在壳子之内者也，十二经络皆在壳子之外者也。然
此壳子又有浅深不同，今分列于后。
第一层为太阳所行之地，手太阳二，足太阳二，阳跷二，督脉一，凡七脉为卫气极盛之
地。
第二层为阳明所行之地，手阳明二，足阳明二，凡四脉为卫气总汇之地。
第三层为少阳所行之地，手少阳二，足少阳二，凡四脉为卫气初出之地。
以上三层皆名为表，少阳近里，为半表半里之界。
第四层为太阴所行之地，手太阴二，足太阴二，凡四脉为卫气初退之地。
第五层，为少阴所行之地，手少阴二，足少阴二，凡四脉为卫气退藏之地（任脉亦在此
层，当云五脉）。
第六层为厥阴所行之地，手厥阴二，足厥阴二，凡四脉为阴尽阳生之地（过此则入脏矣）
。
以上三层皆名为里。
凡卫行脉外者，用此察浅深，详后论卫气篇，知此则知偏枯之风专在卫矣。
凡十二经脉，各有支脉通于脏腑者，名为络，凡风之入脏者由此。
凡十二经脉，其阴经、阳经相交接处，名为交经别络（如手太阴交手阳明，足阳明交足
太阴之类）。其阳经交阳经者在头，阴经交阴经在腹，则无别络。
凡十二经脉，各有小脉从气穴旁出者，名为孙络（又名小络，又名血络）。共有三百六十
五气穴，即有三百六十五孙络。其病最轻。
(This is the pathway of Wei Qi. Wei Qi circulates outside the vessels.)
The human head and extremities form an outer shell, within which reside the Zang-Fu organs (viscera), while the Twelve Primary Meridians lie outside this shell. However, this shell varies in depth, which are listed below.
The first layer is the domain of the Taiyang Meridians (Greater Yang), comprising two Hand-Taiyang meridians, two Foot-Taiyang meridians, two Yang Qiao vessels, and one Du vessel, totaling seven vessels. This is where Wei Qi is most vigorous.
The second layer is the domain of the Yangming Meridians (Bright Yang), comprising two Hand-Yangming meridians and two Foot-Yangming meridians, totaling four vessels. This is where Wei Qi converges.
The third layer is the domain of the Shaoyang Meridians (Lesser Yang), comprising two Hand-Shaoyang meridians and two Foot-Shaoyang meridians, totaling four vessels. This is where Wei Qi initially emerges to the exterior.
These three layers are collectively termed "Exterior" (Biao). The Shaoyang is closer to the interior, forming the boundary of the Half-Exterior Half-Interior (Ban Biao Ban Li).
The fourth layer is the domain of the Taiyin Meridians (Greater Yin), comprising two Hand-Taiyin meridians and two Foot-Taiyin meridians, totaling four vessels. This is where Wei Qi begins to recede.
The fifth layer is the domain of the Shaoyin Meridians (Lesser Yin), comprising two Hand-Shaoyin meridians and two Foot-Shaoyin meridians, totaling four vessels. This is where Wei Qi retreats and stores (the Ren vessel also resides in this layer, making it five vessels in total).
The sixth layer is the domain of the Jueyin Meridians (Terminal Yin), comprising two Hand-Jueyin meridians and two Foot-Jueyin meridians, totaling four vessels. This is where Yin exhausts and Yang generates (beyond this point, the path enters the Zang organs).
These three layers are collectively termed "Interior" (Li).
For cases where Wei Qi circulates outside the vessels, this method can be used to assess depth; detailed discussions are found in the subsequent chapter on Wei Qi. Understanding this reveals that hemiplegic wind-stroke primarily affects the Wei Qi.
Whenever the Twelve Primary Meridians have branch vessels connecting to the Zang-Fu organs, they are called Luo Vessels (Collaterals). Pathogenic Wind invading the Zang organs does so through these Luo Vessels.
At the junctions where Yin and Yang meridians intersect within the Twelve Primary Meridians, they are referred to as Intersecting Collaterals (Jiao Jing Bie Luo) (e.g., the Hand-Taiyin intersects with the Hand-Yangming, the Foot-Yangming intersects with the Foot-Taiyin). Where Yang meridians intersect with Yang meridians, it is in the head; where Yin meridians intersect with Yin meridians, it is in the abdomen; in these specific intersections, there are no separate collaterals.
Each of the Twelve Primary Meridians has small vessels branching out from the sides of acupoints, known as Sun Luo (Branch Collaterals) (also called Xiao Luo or Blood Collaterals). There are 365 acupoints, corresponding to 365 Sun Luo. Diseases affecting these are the mildest.