肺居西方金位。上应阳明燥令。其与足太阴脾同名太阴者。以其为一身元气之主。出治节以佐君。其位居华盖之顶。
其职与太阴脾。同行气以给众脏。故名之也。而其实为阳中之少阴。主秋令以成万物。秋令清肃 敛。肺以丽水之金。
生形而居天河之上源。以沛雨露。故尝病躁与寒热。最为娇脏也。其气恒下行。静则下沉于肾宫。而与水相通。所谓母
隐子胎也。以其外应皮毛。皮毛属太阳之部。故太阳之伤风伤寒。与汗出中风。兼形寒饮冷。皆伤肺见症。如鼻塞声重。
气逆喘嗽。肩背痛。嚏呕胸满烦心等证。多与太阳同。至若五志之火上炎。阴虚内铄。肝火抉心而刑金。则亦伤肺。其
证为肺痈、肺痿、痿 、吐血、声嘶、息有音、鼽衄、掌中热、喘不休、白血出、皮毛焦。此皆火燥焦枯之症。虚则少
气。不能报息。耳聋嗌干。治之之法。伤于外者。与足太阳同法。其邪气盛。而闭塞愤郁。必于足太阳泻之。伤于内者。
正气衰而金被伤。必于足少阴养之。而于足太阴培之。补水培土。养金之善法也。然以金性下沉。隐于子胎。肾家水火
两病。亦能使肺两症同受。故有时水泛而为喘壅。有时水沸而为痰鸣。皆以气上逆。而有水火虚实之不同。而要其治。
总不出足太阳及少阴太阴三经之法耳。
The Lung resides in the West, corresponding to the Metal position. It corresponds superiorly to the Yangming dryness climate. Its shared name "Taiyin" (Greater Yin) with the Foot-Taiyin Spleen is because it serves as the master of the body's primordial Qi, issuing regulatory functions (Zhi Jie) to assist the Sovereign (Heart). Its location is at the apex of the "Huagai" (Canopy, referring to the Lung covering the other organs).
Its function is identical to that of the Foot-Taiyin Spleen: both circulate Qi to supply the various Zang organs, hence their shared name. However, essentially, it belongs to Shao Yin (Lesser Yin) within Yang, governing the Autumn season to complete all things. The Autumn climate is clear,肃 (solemn/clear), and contracting. The Lung, like Metal from Lishui, generates form and resides at the upper source of the Heavenly River (referring to the upper pathways of Qi and Blood), distributing rain and dew (metaphor for the dissemination of Body Fluids). Therefore, it is prone to disorders of restlessness and alternating cold and heat, making it the most delicate organ.
Its Qi naturally descends; when still, it sinks into the Kidney Palace, connecting with Water. This is referred to as "the Mother hiding in the Child's womb" (Lung is the Mother of Kidney, implying mutual generation and storage). Because the Lung externally corresponds to the Skin and Hair, which belong to the Taiyang (Greater Yang) domain, injuries to Taiyang such as Wind Strike (Shang Feng), Cold Damage (Shang Han), wind invasion after sweating, combined with external cold exposure or consumption of cold drinks, all damage the Lung and manifest symptoms. These include nasal congestion with heavy voice, rebellious Qi with wheezing and cough, shoulder and back pain, sneezing with vomiting, chest fullness, and vexation. Such syndromes are largely similar to Taiyang disorders.
However, if the Fire of the Five Emotions flares upward, or Yin deficiency causes internal burning, or Liver Fire joins Heart Fire to attack Metal (Lung), the Lung is also damaged. Manifestations include Lung Abscess (Fei Yong), Lung Withering (Fei Wei), flaccidity syndrome (Wu Zhong), hemoptysis, hoarseness, noisy respiration, rhinorrhea or epistaxis, heat in the palms, incessant wheezing, expectoration of white sputum, and withered skin and hair. These are all symptoms of scorching and drying due to Fire and Dryness. Deficiency leads to shortness of breath and inability to complete inhalation, deafness, and dry throat.
The treatment method: For external injury, the approach is the same as for the Foot-Taiyang Bladder channel. If pathogenic Qi is excessive, causing obstruction and stagnation, purgation must be applied to the Foot-Taiyang channel. For internal injury, where Righteous Qi is deficient and Metal (Lung) is damaged, nourishment must be applied to the Foot-Shaoyin Kidney channel, and tonification to the Foot-Taiyin Spleen channel. Nourishing Water and cultivating Earth are excellent methods for supporting Metal.
However, since the nature of Metal is to sink and hide in the Child's (Kidney's) womb, diseases of both Water and Fire in the Kidney can cause the Lung to suffer from dual pathologies. Thus, sometimes water flooding leads to wheezing and oppression; sometimes boiling water (deficient fire) leads to phlegm rales. All result from rebellious Qi ascending, differing in terms of Water/Fire and Excess/Deficiency. Nevertheless, the general treatment principle never deviates from the methods of the Foot-Taiyang, Foot-Shaoyin, and Foot-Taiyin channels.