To correct the harmful effect of the medicine: let the medicine be compounded when it is contrary to the disease and when it has an evil effect on the member where the disease is located; as for instance scammony which harms the stomach and liver, so that it is necessary to mix black pepper and anise with it.
To strengthen the medicine: let the medicine be compounded when it is weak as is obvious in the case of iris being mixed with theriac, and acorus5 with agaric.