Qibo answered, “Please allow me to explain in order to define the principles [of acupuncture]，from one to nine* Please allow me to explain the rules. The principle of [using] small needles [to treat diseases] is easy to describe but difficult to be mastered. Ordinary [doctors] just stick to the Xing[l1 while ex-cellent [doctors] closely observe the Shen[2]. The so - called Shen [indicates that excellent doctors pay much attention to the struggle between Zhengqi (Healthy - Qi) and Xieqi (Evil - Qi) ] at the entrance [of a certain Channel]. How [could a doctor] know the cause [of a disease if he] does not carefully analyze [the patho¬logical changes of] the disease? The key of acupuncture lies in the rapid and slow [ manipulations of the needle ]. Ordinary [ doctors ] only stick to [the Acupoints located on] the joints [of the four limbs] • [But] excellent [doctors carefully] observe the changes [of Qi movement], The movement [of Qi] cannot deviate from the Acupoints. The movement [of Qi] inside the Acupoints is quiet and insensible- When coming，it cannot be confronted; when receding, it cannot be chased131 . [Those who] are aware of the changes [of Qi movement] make no errors [in applying the rein¬forcing and reducing techniques while those who] are unaware of such changes act just as if holding the arrow without knowing when to shoot it. Only [when one] knows [when it] comes and recedes [can he understand] the right time [of needling] . Unskillful [doctors] are ignorant of [this mechanism] . Only excellent [doctors ] can understand this mystery. The receding [ activity ] means Ni (adverse) while the coming [activity] means Shun (due) . [When one has] understood [the rules of] Ni(adverse) and Shun (due)， [he can] practice [acupuncture] without any doubt. To needle in line with [the running direction of the Channel] will certainly reduce [Xieqi (Evil - Qi) ] while to nee¬dle against [the running direction of the Channel] will surely re¬inforce [Zhengqi (Healthy — Qi) ] - [Whether to needle] in light with [the running direction of the Channel or to needle] against [the running direction of the Channel] requires careful consider¬ation. This is a full explanation of acupuncture principle. ”