实之与虚，若有若无。何谓也？
滑氏曰∶出《灵枢》第一篇∶得，求而获也；失，纵也、遗也。其第二篇曰∶言实与虚
，若
有若无者，谓实者有气，虚者无气也。言虚与实，若得若失者，谓补者必然若有得也，泻者
然若有失也。即第一篇之义。
然迎而夺之者，泻其子也。随而济之者，补其母也。假令心病泻手心主俞，是谓迎而夺
之者也。补手心主井，是谓随而济之者也。
滑氏曰∶迎而夺之者泻也，随而济之者补也。假令心病，心火也，土为火之子，手心主
之俞
太陵也，实则泻之，是迎而夺之也。木者火之母，手心主之井中冲也，虚则补之，是随而济
之也。迎者迎于前，随者随其后。此假心为例而补泻，则云手心主，即《灵枢》所谓少阴无
俞者也，当与六十六难并观。洁古曰∶呼吸出纳，亦名迎随也。
所谓实之与虚者，牢濡之意也。气来实牢者为得，濡虚者为失，故曰若得若失也。
滑氏曰∶气来实牢濡虚，以随济迎夺而为得失也。前云虚之为实，若得若失，实之与虚
The changes between excess (Shi) and deficiency (Xu) appear as if present or absent. What does this mean?
Hua Shou (Master Hua) states: This originates from the first chapter of *Ling Shu* (Spiritual Pivot): "De" (obtaining) means to seek and acquire; "Shi" (losing) means to let go or miss. The second chapter of that text says: Regarding "excess and deficiency, appearing as if present or absent," it refers to the fact that in an excess pattern, there is Qi, whereas in a deficiency pattern, there is no Qi. Regarding "deficiency and excess, appearing as if obtained or lost," it means that after applying tonification (Bu), one inevitably feels as though something has been gained; after applying sedation (Xie), one feels as though something has been lost. This aligns with the meaning of the first chapter.
However, "Ying Er Duo Zhi" (meeting and depriving) refers to sedating the son-needle; "Sui Er Ji Zhi" (following and assisting) refers to tonifying the mother-needle. For example, in heart disease, sedating the Shu-stream point of the Pericardium Meridian of Hand-Jueyin (Neiguan/Tailing context implies Tailing here) is called "Ying Er Duo Zhi." Tonifying the Jing-well point of the Pericardium Meridian of Hand-Jueyin (Zhongchong) is called "Sui Er Ji Zhi."
Hua Shou states: "Ying Er Duo Zhi" is sedation; "Sui Er Ji Zhi" is tonification. Taking heart disease as an example, the Heart belongs to Fire, and Earth is the son of Fire. The Shu-stream point of the Pericardium Meridian is Tailing (PC7); when there is excess, sedating it constitutes "Ying Er Duo Zhi." Wood is the mother of Fire; the Jing-well point of the Pericardium Meridian is Zhongchong (PC9); when there is deficiency, tonifying it constitutes "Sui Er Ji Zhi." "Ying" (meeting) occurs ahead [against the flow], while "Sui" (following) occurs behind [with the flow]. This uses the Heart as an example to illustrate tonification and sedation; mentioning the Pericardium Meridian here corresponds to the concept in *Ling Shu* that "Shaoyin has no Shu points." It should be read in conjunction with Chapter 66 of *Nan Jing*. Li Gao (Jiegu) stated: The exhalation and inhalation during breathing are also referred to as "Ying Sui" (Meeting and Following).
What is meant by "excess and deficiency" is the distinction between firmness and softness. When the Qi arrives firmly and solidly, it is "obtained"; when it is soft and deficient, it is "lost." Hence, it is said to be "as if obtained or lost."
Hua Shou states: The firmness/solidity or softness/deficiency of the arriving Qi manifests as "obtaining" or "losing" through the techniques of "Sui Ji" (following-assisting) and "Ying Duo" (meeting-depriving). Previously mentioned was the transformation from deficiency to excess, resembling "as if obtained or lost," and the interplay of excess and deficiency...