Difficulty 71

The medical classic says: When needling the nutritive (ying) level, do not harm the defensive (wei) level; when needling the defensive level, do not harm the nutritive level. What does this mean?

Answer: When needling the defensive level, which pertains to yang, insert the needle with the body lying flat (inserting along the skin). When needling the nutritive level, which pertains to yin, first press with the left hand on the region of the Ying-spring and Shu-stream points to be needled, causing the local qi and blood to disperse before inserting the needle. This is called "needling the nutritive level without harming the defensive level, and needling the defensive level without harming the nutritive level."