二十六难曰∶经有十二，络有十五，余三络者，是何等络也？
然∶有阳络，有阴络，有脾之大络。
阳络者阳跷之络也。阴络者，阴跷之络也。故络有十五焉。
十二经有十二络，如手太阴络大肠，手阳明属大肠络肺之类。此云络有十五者，以阳跷之络统诸
阳，阴跷之络统诸阴，又以脾之大络总统阴阳诸络也。
按∶《灵枢·经脉篇》，十二经别之外，以督脉之长强，任脉之尾翳，脾之大包，合为十五
络。盖督脉统络诸阳，任脉统络诸阴，以为十二经络阴阳之纲领故也。若阳跷为足太阳之别，阴跷为足
少阴之别，不能统诸阴阳。越人取此，或别有见义，未可知也。
然∶《素问·平人气象论》云∶胃之大络，
名曰虚里，贯膈络肺，出于左乳下，其动应衣，脉宗气也。虚里一穴，为胃之大络，若动甚则宗气泄矣，
是亦不可不知也。夫十二经脉之血气与脉，皮肤之气血，皆生于胃腑水谷之精，而各走其道。经脉十二者，
六脏六腑，手足三阴三阳之脉，乃营血营行，伏于分肉之内，始于手太阴肺，终于足厥阴肝，周而复始，
以应呼吸漏下者也。即西医所谓运血之脉管也。其出于孙络皮肤者，随三焦出气，溢于孙络，以充肤热肉，
澹渗毫毛，卫行于周身，即西医所谓之微丝血管也。由孙络行遍周身，溜于经别。经别者，脏腑之络脉也。
与经脉交相逆顺而行，即西医所谓回血管也。人身经脉十二，络脉十五，二十七气出入，阴阳相贯，如环
之无端。任脉统一身之阴以主出，督脉统一身之阳以主入，两跷即随经脉交相逆顺，而行之阳络阴络也。
Difficulty 26 states: There are twelve meridians and fifteen collaterals. What are the three extra collaterals?
The response is: There are the Yang Qiao collateral, the Yin Qiao collateral, and the Great Collateral of the Spleen.
The so-called Yang Luo (Yang Qiao Collateral) refers to the collateral of the Yang Qiao Mai (Yang Heel Vessel). The so-called Yin Luo (Yin Qiao Collateral) refers to the collateral of the Yin Qiao Mai (Yin Heel Vessel). Thus, there are fifteen collaterals in total.
Each of the twelve regular meridians has its own collateral, totaling twelve. For example, the collateral of the Hand Taiyin Lung Meridian connects to the Large Intestine, and the collateral of the Hand Yangming Large Intestine Meridian connects to the Lung. The reason for stating there are fifteen collaterals here is that the Yang Qiao collateral governs all yang collaterals, the Yin Qiao collateral governs all yin collaterals, and the Great Collateral of the Spleen oversees all yin and yang collaterals.
Commentary: In the "Jingmai" chapter of *Ling Shu* (Spiritual Pivot), besides the twelve divergent meridians, the Changqiang (GV1) point of the Du Mai (Governing Vessel), the Wei Yi (CV15, also known as Jiutui) point of the Ren Mai (Conception Vessel), and the Dabao (SP21) point of the Spleen are combined to form the fifteen collaterals. This is because the Du Mai governs and connects all yang meridians, and the Ren Mai governs and connects all yin meridians, serving as the general outline for the yin and yang of the twelve meridians and collaterals. If one considers that the Yang Qiao is a branch of the Foot Taiyang Bladder Meridian and the Yin Qiao is a branch of the Foot Shaoyin Kidney Meridian, they cannot govern all yin and yang meridians. It is uncertain whether Yue Ren (Bian Que) selected these two for other profound reasons.
Response: The *Su Wen* (Basic Questions) chapter "Ping Ren Qi Xiang Lun" (Treatise on the Normal Pulse Phenomena of Healthy Persons) states: The great collateral of the Stomach is named Xuli. It penetrates the diaphragm, connects with the Lung, and emerges below the left nipple. Its pulsation is visible through clothing; this is the Zong Qi (Pectoral Qi / Gathering Qi) of the pulse. The Xuli point serves as the great collateral of the Stomach. If its pulsation is excessively vigorous, it indicates the leakage of Zong Qi, which is something one must not ignore.
The blood and qi of the twelve regular meridians and the pulse, as well as the qi and blood of the skin, all originate from the refined essence produced by the Stomach and Intestines from food and water, each traveling along its respective pathway. The twelve meridians correspond to the six zang organs and six fu organs, comprising the hand and foot three yin and three yang meridians. Ying Blood (Nutritive Blood) travels with Ying Qi (Nutritive Qi), lying hidden within the muscle intervals. It begins at the Hand Taiyin Lung Meridian and ends at the Foot Jueyin Liver Meridian, circulating continuously to correspond with respiration and timekeeping. This corresponds to what Western medicine calls blood vessels. Those emerging from the Sunluo (Sun Collaterals) and distributing into the skin travel outward with Sanjiao Qi (Triple Energizer Qi), overflowing into the Sunluo to nourish the skin and flesh, moisten the hair, and allow Wei Qi (Defensive Qi) to circulate throughout the body. This corresponds to what Western medicine calls capillaries. From the Sunluo, they traverse the entire body and flow into the Jingbie (Divergent Meridians). The Jingbie are the collateral networks of the zang and fu organs. They run in alternating reverse and forward directions relative to the regular meridians, corresponding to what Western medicine calls venous return or veins. The human body has twelve regular meridians and fifteen collaterals. The twenty-seven qi (twelve meridians plus fifteen collaterals) enter and exit, with yin and yang interpenetrating like a circle without beginning or end. The Ren Mai unifies the yin of the whole body to govern outgoing movement, and the Du Mai unifies the yang of the whole body to govern incoming movement. The two Qiao vessels follow the regular meridians, running in alternating reverse and forward directions; these are the so-called Yang Luo and Yin Luo.