《伤寒论·辨厥阴病脉证并治》
虚寒腹泻，出现脉数而口渴的，是阳气回复，其病将要痊愈。假如不痊愈，则是阳热有余，势必引起大便下脓血。
下利，脉数而渴者，今自愈；设不差，必清脓血，以有热故也。
Diarrhea due to deficiency of qi and yang leads to rapid pulse and thirst, indicating the recovery of yang qi and the approaching recovery from the disease. If not recovered, it is due to excessive yang heat, which will inevitably lead to bloody stools.