81th difficulty of Nanjing explains that disease of excess or deficiency of meridians of the body can't be diagnosed through cunkou. Same conclusion achieved in 8th difficult issue. Chicun is the pulse area where excess or deficiency may be found.
81th difficulty explains also rule of supplementation and depletion, evoiding harm by supplementing the full and depleting the empty.
A. As an example difficulty shows liver excess and lung deficiency treating directly affected meridians. Liver is a son for kidney, so it depletes kidney. Liver is mother for heart, so it supplement the heart. Treatment of the liver will deplete kidney, supplement heart and heart through controlling connection will deplete even more depleted lung.
As an example of excessive lung and deficient liver. Example shows again direct treatment of the lung. Lung is a son of the spleen, so it will deplete the spleen. Lung is a mother for the kidney, it will supplement kidney. There will be no effect on liver except lung will be depleting already depleted liver even more through controlling ko connection, Liver can't control spleen, so excess of spleen will supplement even more excess of lung​
​B. Archaic acupuncture explains method of needling in difficulty 69 of Nanjing. 
In the case of liver excess and lung deficiency, treatment should be directed towards the spleen. Spleen is a mother of the lung, so it will be supplementing the lung. Spleen is a son of the heart, so it will be depleting the heart, decreasing heart's ko connection which controls the lung. Supplemented lung will decrease excess of liver through ko controlling connection. This treatment will supplement depleted lung and deplete excessive liver.
In the case of lung excess and liver deficiency treatment should be directed towards the kidney. Kidney is a mother of the liver, so it will be supplementing liver's deficiency. Kidney is a son of the lung, so it will be depleting excess of the lung. Liver becoming stronger will increase its control over the spleen, so spleen will not be feeding excess of the lung. This treatment depletes excess and supplement deficiency.
​This difficulty is linked with difficulty 75 which provides with one extra step towards successful supplementing of deficiency and depleting of excess.