凡损伤元气者，本皆虚症，而古方以虚损劳瘵，各分门类，则病若有异，亦所宜辨。
之虚，有在阳分，有在阴分，其病尚浅，或用益火，或用滋阴，见症施治，各有宜也。至若
劳瘵，则或为骨蒸，或为干嗽，吐血吐痰，营卫俱败， 羸日甚，其病深在阴中之阴分，多
有不宜温补者。此虚与劳，似乎各有分别。然要而论之，则劳瘵之症，特不过阴虚之极深极
重者耳！凡阴虚用药失当，或误用辛温，或妄投消伐，遂至日甚而成瘵矣，有不可不慎也。
不论阴阳，虚损日久，皆能传变。有谓男子自肾传心肺肝脾，女子自心传肺肝脾肾者
，此其说不可信也。《难经》云∶损脉为病，一损损于皮毛，皮聚毛落；二损损于血脉，血
，不能营于五脏六腑；三损损于肌肉，肌肉消瘦，饮食不为肌肤；四损损于筋，筋缓不能自
收持；五损损于骨，骨痿不能起床。反此者，至脉之病也。从上下者，骨痿不能起于床者死
。从下上者，皮聚毛落者死。观此上损下损之说，其义极精。盖凡思虑劳倦外感等症则伤阳
，伤于阳者，病必自上而下也。色欲醉饱内伤等症则伤阴，伤于阴者，病必自下而上也。自
上而下者，先伤乎气，故一损于肺，而病在声息肤腠；二损于心，而病在血脉颜色；三损于
胃，而病在饮食不调；四损于肝，而病为 疼痛；五损于肾，而病为骨痿。二便不禁，此
先伤乎阳，后及乎阴，阳竭于下，则孤阴无以独存，而不可为也。自下而上者，先伤乎精，
故一损于肾，而病为泉源干涸；二损于肝，而病为血动筋枯；三损于脾，而病为痰涎壅盛；
四损于心，而病为神魂失守；五损于肺，而病为短气喘呼。此先伤乎阴，后及乎阳，阴竭于
上，则孤阳无以独存，而不可为也。然二者之损，又皆以脾胃为生死之大关，盖脾胃者土也
，万物之本也。若上过乎此，则传肝传肾，不可治矣。下过乎此，则传心传肺，不可治矣。
故曰∶心肺损而神衰，肝肾损而形敝，脾胃损而饮食不归血气。夫迨其传变已深，而希望回
生，不已晚乎！所贵君子者，亦在乎防微杜渐而已。
凡是损伤元气的人，本质上都是虚证，但古方将虚损和劳瘵分别归类，说明病症虽有不同，也是应当加以辨别的。
虚证，有的在阳分，有的在阴分，病情尚浅，有的可以用益火法（温补阳气），有的可以用滋阴法（滋养阴液），根据症状施治，各有适宜的方法。至于劳瘵，则有的表现为骨蒸（阴虚发热如从骨内透发而出），有的表现为干咳、吐血或吐痰，营卫之气都败坏，身体日益消瘦，病情深在阴中之阴分，大多不宜使用温补法。这虚证与劳瘵，似乎各有区别。然而概括来说，劳瘵的病症，只不过就是阴虚到了极深极重的程度罢了！凡是阴虚用药不当，或者误用辛温药物，或者妄投消伐药物，于是导致病情日益加重而成为劳瘵，这是不可不谨慎的。
不论阴阳，虚损日久，都能发生传变。有人说男子病变从肾传至心肺肝脾，女子病变从心传至肺肝脾肾，这种说法是不可信的。《难经》说：损脉所致的疾病，一损损害皮毛，皮肤聚拢、毛发脱落；二损损害血脉，血液减少，不能营养五脏六腑；三损损害肌肉，肌肉消瘦，饮食不能转化为肌肤营养；四损损害筋，筋脉弛缓不能自主收持；五损损害骨，骨痿弱不能起床。与此相反的是至脉的病证。从上往下传的，出现骨痿不能起床的预后不良（死）。从下往上传的，出现皮聚毛落的预后不良（死）。观察这种上损和下损的说法，其义理极其精妙。大概思虑、劳倦、外感等病症会伤阳，伤于阳的，病势必定自上而下发展。色欲、醉饱等内伤病症会伤阴，伤于阴的，病势必定自下而上发展。自上而下发展的，先伤气，所以一损在肺，病在声音气息和皮肤腠理；二损在心，病在血脉颜色；三损在胃，病在饮食不调；四损在肝，病为胁痛；五损在肾，病为骨痿、大小便失禁。这是先伤阳，后及于阴，阳气竭绝于下，那么孤阴无法独自存在，就无法救治了。自下而上发展的，先伤精，所以一损在肾，病为源泉干涸；二损在肝，病为血动筋枯；三损在脾，病为痰涎壅盛；四损在心，病为神魂失守；五损在肺，病为短气喘呼。这是先伤阴，后及于阳，阴液竭绝于上，那么孤阳无法独自存在，就无法救治了。然而这两种损伤，又以脾胃为生死的关键大关，因为脾胃属土，是万物的根本。如果病势超过这个界限向上发展，就会传至肝、肾，就无法治疗了。如果病势超过这个界限向下发展，就会传至心、肺，也无法治疗了。所以说：心肺受损则神气衰微，肝肾受损则形体敝坏，脾胃受损则饮食不能化生为血气。等到传变已经深入，才希望起死回生，不是太晚了吗！可贵之处在于君子能够防微杜渐罢了。
Any condition that damages the Yuan Qi (Original Qi) is fundamentally a deficiency syndrome. However, ancient texts classified Xu Sun (Deficiency and Wasting) and Lao Zhai (Consumptive Disease) into separate categories, indicating that although the diseases may appear different, they warrant distinct differentiation.
Deficiency syndromes can occur in the Yang aspect or the Yin aspect. When the pathology is still superficial, treatment may involve Yi Huo (Warming and Supplementing Fire/Yang) or Zi Yin (Nourishing Yin), with therapeutic strategies tailored to specific manifestations, each having its appropriate application. In contrast, Lao Zhai (Consumptive Disease) may present as Gu Zheng (Bone-steaming fever, a sensation of heat emanating from the bones due to Yin deficiency), dry cough, hemoptysis (coughing up blood), or expectoration of phlegm. In such cases, both Ying Wei (Nutritive and Defensive Qi) are exhausted, and emaciation worsens daily. The pathology is deep within the Yin-to-Yin aspect, and warm-tonifying methods are generally contraindicated. Thus, Xu (Deficiency) and Lao (Consumption) seem to have distinct differences. However, summarizing them, Lao Zhai (Consumptive Disease) is merely an extreme and severe stage of Yin deficiency! If medication for Yin deficiency is inappropriate—such as mistakenly using Xin Wen (Acrid-Warm herbs) or recklessly administering Xiao Fa (Draining and Reducing methods)—the condition will deteriorate daily until it becomes Lao Zhai (Consumptive Disease). Therefore, caution is essential.
Regardless of whether the injury involves Yin or Yang, prolonged deficiency and wasting can lead to disease transmission. Some claim that in men, disease transmits from the Kidney to the Heart, Lung, Liver, and Spleen, while in women, it transmits from the Heart to the Lung, Liver, Spleen, and Kidney; this theory is unreliable. The *Nan Jing* (Classic of Difficult Issues) states: Diseases caused by Sun Mai (Diminished Pulse) manifest as follows: First degree of damage affects the skin and hair, causing skin contraction and hair loss; second degree affects the blood vessels, leading to blood insufficiency unable to nourish the five zang and six fu organs; third degree affects the muscles, causing muscle emaciation where food intake fails to build flesh; fourth degree affects the sinews, causing flaccidity and inability to hold oneself upright; fifth degree affects the bones, causing bone atrophy and inability to rise from bed. The reverse progression characterizes the Zhi Mai (Excessive/Extreme Pulse) disease. Transmission from upper to lower levels, culminating in bone atrophy preventing one from rising from bed, indicates death. Transmission from lower to upper levels, culminating in skin contraction and hair loss, also indicates death. Observing these concepts of upper and lower damage reveals profound logic. Generally, conditions such as mental overwork, fatigue, and external pathogenic invasions injure Yang; injuries to Yang inevitably progress from top to bottom. Conditions such as sexual excess and overindulgence in food and alcohol injure Yin; injuries to Yin inevitably progress from bottom to top.
Progression from top to bottom first injures Qi. Thus, the first degree of damage in the Lung manifests as abnormalities in voice, respiration, skin, and interstices; the second degree in the Heart manifests as abnormalities in blood vessels and complexion; the third degree in the Stomach manifests as dietary irregularities; the fourth degree in the Liver manifests as hypochondriac pain; and the fifth degree in the Kidney manifests as bone atrophy and incontinence of urine and feces. This represents initial injury to Yang followed by involvement of Yin. When Yang exhausts at the lower level, isolated Yin cannot survive alone, rendering the condition untreatable. Progression from bottom to top first injures Essence. Thus, the first degree of damage in the Kidney manifests as the drying up of the source (essence); the second degree in the Liver manifests as restless blood and withered sinews; the third degree in the Spleen manifests as abundant phlegm and saliva; the fourth degree in the Heart manifests as loss of spirit and mind control; and the fifth degree in the Lung manifests as shortness of breath and wheezing. This represents initial injury to Yin followed by involvement of Yang. When Yin exhausts at the upper level, isolated Yang cannot survive alone, rendering the condition untreatable.
However, both types of damage regard the Spleen and Stomach as the critical juncture for life and death. Since the Spleen and Stomach belong to Earth, they are the root of all things. If the pathological transmission exceeds this point upward, it spreads to the Liver and Kidney, becoming untreatable. If it exceeds this point downward, it spreads to the Heart and Lung, also becoming untreatable. Therefore, it is said: Damage to the Heart and Lung leads to decline of Shen (Spirit); damage to the Liver and Kidney leads to deterioration of Xing (Form); damage to the Spleen and Stomach prevents food from transforming into Blood and Qi. By the time transmission has progressed deeply, hoping for recovery is already too late. The value of a wise person lies precisely in preventing problems before they arise (Fang Wei Du Jian).