Similar to the seasonal differences that affect the pulse, the seasons also affect the location of the acupuncture point. The more Yang energy present in the environment, the more superficial the location of the acupuncture point. Ling Shu, chapter nineteen discusses the impact that the season has on the acupuncture point depth.
Huang Di asked Qi Bo, “The energy of each of the four seasons is different, [each one] can cause diseases to arise, how does one decide the proper acupuncture technique?” Qi Bo replies, “The energy of the four seasons has its own location that will influence the acupuncture method used to reach the acupuncture points. Therefore, during spring aim for the space between the blood vessel and the muscle, needle deep for a severe disease, needle shallow for a less severe disease. During summer recognize that the meridians and superficial collaterals are full, stop the insertion just after penetrating the skin. During autumn choose the Jing and Shu points, [if] the disease affects the Fu organs, use the He point. During winter select the Jing (Well) and Ying points, they must be needled deeply and the needle must be retained longer.”
In the previous passage the proper insertion depth is revealed for two seasons, spring and summer. These seasons have the most Yang energy. In spring the point is located under the skin, yet above the muscle. This is described as being at the same level of the vessels. During summer the energy of the season fills the body and raises the point location to precisely under the skin at the level of the superficial collaterals. The first layer under the skin is designated as the superficial collateral level. Deeper, lies the muscle and the bone level, but they were not mentioned in this passage. Therefore, the depths of autumn and winter are not given here.
Su Wen, chapter sixty-four provides the missing depths. “秋刺经脉，血气上逆，令人善忘；秋刺络脉，气不外行，令人卧不欲动；秋刺筋骨，血气内散，令人寒慄。” “Inserting the needle to the depth of the vessels during autumn reverses the qi and blood flow upward, causes people to become extremely forgetful, or amnesia; inserting the needle to the depth of the superficial collaterals blocks the outward flow of Qi, causes people to lie down and not want to move; to needle down to the tendons and the bone during autumn will scatter the Qi and blood, causing people to feel cold and tremble.” By mere exclusion, the only safe depth during autumn is the muscle level. Ling Shu, chapter nine also offers this statement, “秋气在分肉。” “The Qi is between the muscles during autumn.”1
The proper insertion depth during winter is obvious. The chapter begins with this passage, “冬气在骨髓中。” “[During] winter the Qi is in the bone marrow.” This refers to the philosophy that during winter the body’s energy contracts and sinks to its deepest depths. Later in the chapter the same list of contraindications is given about needling during winter. Even though the passage says the energy is inside the bone, the acupuncture point is located just above the bone. This conclusion is made because of the sheer improvability of needling into the bone, but also to the statement made in Ling Shu, chapter one, “Each acupuncture point is located where the qi drifts and flows out and in, below the skin, between the muscles, along side the tendons, and above the bones.” So, to follow the words of Nei Jing, one must insert the needle to a depth, just above the bone, during winter.
Summer: Superficial Collateral Level
Spring: Vessel Level
Autumn: Muscle Level
Winter: Bone Level
Figure 1: Table of needle insertion depth according to the season. The skin is the most superficial level, bone level is the deepest.
1 Su Wen, chapter sixty-four provides a serious dilemma for the reader. The beginning of the chapter lists five seasons, which includes the long summer. This addition is logical according to Five Element philosophy. But, the depth of needle insertion during long summer is designated as being the muscle level. This designation does not match the logical progression laid out in the rest of Nei Jing regarding acupuncture point depth. There is reprieve later in this chapter. Long summer is no longer mentioned in the second half when the ill effects of improper needling are mentioned. Autumn then, takes the place of long summer as having its acupuncture points located at the muscle and tendon level.