四十九难曰∶有正经自病，有五邪所伤，何以别之？然∶忧愁思虑则伤心，形寒饮冷则
伤肺；恚怒气逆上而不下则伤肝；饮食劳倦则伤脾；久坐湿地，强力入水则伤肾。是正经之
自病也。
何谓五邪？然∶有中风，有伤暑，有饮食劳倦，有伤寒，有中湿。此之谓五邪。
假令心病，何以知中风得之？然∶其色当赤。何以言之？肝主色，自入为青，入心为赤，入脾
为黄，入肺为白，入肾为黑。肝为心邪，故知当赤色。其病身热、胁下满痛。其脉浮大而弦。
何以知伤暑得之？然∶当恶臭。何以言之？心主臭，自入为焦臭，入脾为香臭，入肝为臊臭，
入肾为腐臭，入肺为腥臭。故知心病伤暑得之，当恶臭，其病身热而烦，心痛。其脉浮大而散。
何以知饮食劳倦得之？然∶当喜苦味也。虚为不欲食，实为欲食。何以言之？脾主味，入肝为酸，
入心为苦，入肺为辛，入肾为咸，自入为甘。故知脾邪入心，为喜苦味也。其病身热而体重嗜卧，四
肢不收。其脉浮大而缓。
何以知伤寒得之？然∶当谵言妄语。何以言之？肺主声，入肝为呼，入心为言，入脾为歌，
入肾为呻，自入为哭，故知肺邪入心，为谵言妄语也。其病身热，洒洒恶寒，甚则喘咳。其脉浮大而涩。
何以知中湿得之？然∶当喜汗出不可止。何以言之？肾主湿，入肝为泣，入心为汗，入脾为涎，
入肺为涕，自入为唾。故知肾邪入心，为汗出不可止也。其病身热而小腹痛，足胫寒而逆。其脉沉濡而
大。此五邪之法也。
Difficulty 49 states: There are diseases originating from the regular meridians themselves (Zhengjing Zibing) and those caused by the Five Evils (Wu Xie). How can they be distinguished? The answer is: Worry and overthinking damage the Heart; exposure to cold and consumption of cold drinks damage the Lungs; anger causing Qi rebellion upward without descending damages the Liver; improper diet and overexertion damage the Spleen; sitting long in damp places or forcing oneself into water damages the Kidneys. These constitute the diseases of the regular meridians themselves.
What are the Five Evils? The answer is: Wind-stroke (Zhong Feng), Summerheat injury (Shang Shu), Diet and overexertion, Cold injury (Shang Han), and Dampness invasion (Zhong Shi). This is referred to as the Five Evils.
Suppose a Heart disease occurs; how do we know it is caused by Wind-stroke? The answer is: The complexion should be red. Why? The Liver governs colors. Green enters the Liver (its own organ), Red enters the Heart, Yellow enters the Spleen, White enters the Lungs, and Black enters the Kidneys. Since the Liver acts as the evil for the Heart (Wood generating Fire, implying the pathogenic factor from the mother organ affecting the child), we know the complexion will be red. The symptoms include body heat, fullness and pain under the hypochondrium. The pulse is floating, large, and wiry (Xian).
How do we know it is caused by Summerheat injury? The answer is: There should be aversion to odors. Why? The Heart governs odors. Burnt odor enters the Heart (its own organ), Fragrant odor enters the Spleen, Pungent/Fishy odor enters the Liver, Rotten odor enters the Kidneys, and Fishy odor enters the Lungs. Therefore, knowing that the Heart disease is caused by Summerheat, there should be an aversion to odors. The symptoms include body heat, vexation, and heart pain. The pulse is floating, large, and scattered (San).
How do we know it is caused by diet and overexertion? The answer is: There should be a preference for bitter taste. Deficiency leads to lack of appetite, while Excess leads to desire for food. Why? The Spleen governs tastes. Sour taste enters the Liver, Bitter taste enters the Heart, Acrid/Pungent taste enters the Lungs, Salty taste enters the Kidneys, and Sweet taste enters the Spleen (its own organ). Therefore, knowing that the Spleen's evil enters the Heart, there is a preference for bitter taste. The symptoms include body heat, heavy body, drowsiness, and limbs that cannot be gathered or controlled. The pulse is floating, large, and slow (Huan).
How do we know it is caused by Cold injury? The answer is: There should be delirious speech and妄语 (confabulation/nonsense). Why? The Lungs govern sounds. Crying sound enters the Lungs (its own organ), Calling out enters the Liver, Speaking enters the Heart, Singing enters the Spleen, Moaning enters the Kidneys. Therefore, knowing that the Lung's evil enters the Heart, there is delirious speech. The symptoms include body heat, shivering with aversion to cold, and severe cases may involve wheezing and coughing. The pulse is floating, large, and choppy (Se).
How do we know it is caused by Dampness invasion? The answer is: There should be profuse sweating that cannot be stopped. Why? The Kidneys govern fluids. Tears enter the Liver, Sweat enters the Heart, Saliva (thin) enters the Spleen, Nasal mucus enters the Lungs, and Spittle (thick) enters the Kidneys (its own organ). Therefore, knowing that the Kidney's evil enters the Heart, there is unstoppable sweating. The symptoms include body heat, lower abdominal pain, and coldness with reversal in the feet and calves. The pulse is deep, soggy (Ru), and large. This is the method for distinguishing the Five Evils.