In the classical sequence, the reverting yīn (jué yīn) is the last of the three yīn channels. Hence, it should theoretically be associated with the most severe diseases. Plain Questions (素问 sù wèn), states, The reverting yīn (jué yīn) channel skirts round the genitals and connects with the liver so that diseases include vexation and fullness, and retracted scrotum. The same chapter also mentions, among the signs of reverting yīn (jué yīn) disease, deafness, retraction of the scrotum, inability to ingest [even] liquid foods, and unconsciousness.Plain Questions (素问 sù wèn) enumerates symptoms but prescribes no formulas. Because the reverting yīn (jué yīn) patterns described in On Cold Damage (伤寒论 shāng hán lùn) are less severe, the real nature of reverting yīn (jué yīn) disease is still in question. Further research is required to clarify the matter fully. Reverting yīn (jué yīn) disease as described in On Cold Damage (伤寒论 shāng hán lùn) is characterized by upper body heat and lower body coldand may take the form of dispersion-thirst, qì surging up into the heart region, pain and heat in the heart region, hunger with no desire to eat, or vomiting of roundworm. Reversal cold of the limbs is also observed in some cases. Pathomechanically, upper body heat and lower body cold is explained as a cold-heat complex resulting from interior vacuity. Dispersion-thirst, qì surging up into the heart region, pain and heat in the heart region, and clamoring stomach discomfort are the manifestations of upper body heat (heat in the area just above the diaphragm). No desire for food and vomiting of roundworm reflect lower body cold (in the intestines). This impairs the movement and transformation of the food, which disquiets the roundworm and causes it to rise counterflow. The reversal cold of the limbs indicates failure of yáng qì to reach the periphery of the body, arising when a cold-heat complex disrupts qì dynamic.