十五难曰∶经言春脉弦，夏脉钩，秋脉毛，冬脉石，是王脉耶，将病脉也？然∶弦、钩、毛、石者。
四时之脉也。春脉弦者，肝，东方木也，万物始生，未有枝叶，故其脉之来，濡弱而长，故曰弦。夏脉
钩者，心，南方火也，万物之所茂，垂枝布叶，皆下曲如钩，故其脉之来疾去迟，故曰钩。秋脉毛者，肺
，西方金也，万物之所终，草木华叶，皆秋而落，其枝独在，若毫毛也，故其脉之来，轻虚以浮，故曰毛
。冬脉石者，肾，北方水也，万物之所藏也，盛冬之时，水凝如石，故其脉之来，沉濡而滑，故曰石。此
四时之脉也。如有变奈何？
然∶春脉弦，反者为病。何谓反？然∶其气来实强，是谓太过，病在外；气来虚微，是谓不及，
病在内。气来厌厌聂聂，如循榆叶曰平；益实而滑，如循长竿曰病；急而劲益强，如新张弓弦曰死。
春脉微弦曰平，弦多胃气少曰病，但弦无胃气曰死，春以胃气为本。
夏脉钩，反者为病。何谓反？然∶其气来实强，是谓太过，病在外；气来虚微，是谓不及，病在
内。其脉来累累如环，如循琅 曰平？来而益数，如鸡举足者曰病；前曲后居，如操带钩曰死。夏脉
微钩曰平，钩多胃气少曰病，但钩无胃气曰死，夏以胃气为本。
秋脉毛，反者为病。何谓反？然；其气来实强，是谓太过，病在外；气来虚微，是谓不及，病在
内。其脉来蔼蔼如车盖，按之益大曰平；不上不下，如循鸡羽曰病；按之萧索，如风吹毛曰死。秋脉微毛
曰平，毛多胃气少曰病，但毛无胃气曰死，秋以胃气为本。
冬脉石，反者为病。何谓反？然∶其气来实强，是谓太过，病在外；气来虚微，是谓不及，病在内
。脉来上大下兑，濡滑如雀之啄曰平∶啄啄连属，其中微曲曰病；来如解索，去如弹石曰死。冬脉微石
曰平，石多胃气少曰病，但石无胃气曰死，冬以胃气为本。
胃者，水谷之海，主禀，四时皆以胃气为本。是谓四时之变病，死生之要会也。
脾者，中州也，其平和不可得见，衰乃见耳。来如雀之啄，如水之下漏，是脾衰见也。
Difficulty 15 states: The classic texts mention that the spring pulse is *xian* (string-like), the summer pulse is *gou* (hook-like), the autumn pulse is *mao* (feather-like), and the winter pulse is *shi* (stone-like). Are these the pulses of the thriving seasons (*Wang Mai*, pulses corresponding to the dominant season) or are they pathological pulses? The answer is: *Xian*, *gou*, *mao*, and *shi* are the pulses of the four seasons.
The spring pulse is *xian* because the Liver corresponds to Wood in the East. When all things begin to sprout, there are no branches or leaves yet; thus, the arrival of its pulse is soft, weak, and long, hence it is called *xian*.
The summer pulse is *gou* because the Heart corresponds to Fire in the South. All things flourish at this time; the hanging branches and spreading leaves curve downwards like hooks. Thus, the arrival of its pulse is rapid, and its departure is slow, hence it is called *gou*.
The autumn pulse is *mao* because the Lungs correspond to Metal in the West. All things reach their conclusion at this time; the flowers and leaves of grass and trees fall in autumn, leaving only the branches exposed, resembling fine hairs. Thus, the arrival of its pulse is light, empty, and floating, hence it is called *mao*.
The winter pulse is *shi* because the Kidneys correspond to Water in the North. All things are stored at this time. In deep winter, water freezes as hard as stone. Thus, the arrival of its pulse is deep, soft, and slippery, hence it is called *shi*. These are the pulses of the four seasons. What happens if there are variations?
The answer is: The spring pulse should be *xian*; deviation from this indicates disease. What constitutes a deviation? The answer is: If the Qi arrives solid and strong, it is termed "Excess" (*Tai Guo*), indicating disease in the exterior; if the Qi arrives deficient and faint, it is termed "Deficiency" (*Bu Ji*), indicating disease in the interior.
A normal pulse arrives gently and softly, like feeling elm leaves. A pulse that becomes more solid and slippery, like feeling a long bamboo pole, indicates disease. A pulse that is urgent, forceful, and increasingly rigid, like a newly strung bowstring, indicates death.
A spring pulse that is slightly *xian* indicates health; one that is predominantly *xian* with little Stomach Qi indicates disease; one that is purely *xian* without Stomach Qi indicates death. The spring pulse takes Stomach Qi as its foundation.
The summer pulse should be *gou*; deviation from this indicates disease. What constitutes a deviation? The answer is: If the Qi arrives solid and strong, it is termed "Excess," indicating disease in the exterior; if the Qi arrives deficient and faint, it is termed "Deficiency," indicating disease in the interior.
A normal pulse arrives continuously and roundly, like feeling polished jade. A pulse that becomes more frequent and hurried, like a chicken lifting its feet, indicates disease. A pulse that curves forward and stays rigid backward, like handling a belt hook, indicates death.
A summer pulse that is slightly *gou* indicates health; one that is predominantly *gou* with little Stomach Qi indicates disease; one that is purely *gou* without Stomach Qi indicates death. The summer pulse takes Stomach Qi as its foundation.
The autumn pulse should be *mao*; deviation from this indicates disease. What constitutes a deviation? The answer is: If the Qi arrives solid and strong, it is termed "Excess," indicating disease in the exterior; if the Qi arrives deficient and faint, it is termed "Deficiency," indicating disease in the interior.
A normal pulse arrives grandly like a chariot canopy, becoming larger upon pressure. A pulse that neither rises nor falls, like feeling a chicken feather, indicates disease. A pulse that feels desolate upon pressure, like wind blowing through feathers, indicates death.
An autumn pulse that is slightly *mao* indicates health; one that is predominantly *mao* with little Stomach Qi indicates disease; one that is purely *mao* without Stomach Qi indicates death. The autumn pulse takes Stomach Qi as its foundation.
The winter pulse should be *shi*; deviation from this indicates disease. What constitutes a deviation? The answer is: If the Qi arrives solid and strong, it is termed "Excess," indicating disease in the exterior; if the Qi arrives deficient and faint, it is termed "Deficiency," indicating disease in the interior.
A normal pulse is large above and small below, soft and slippery like a sparrow pecking. A pulse that pecks continuously but has slight irregularities in between indicates disease. A pulse that arrives like an untying rope and departs like a striking stone indicates death.
A winter pulse that is slightly *shi* indicates health; one that is predominantly *shi* with little Stomach Qi indicates disease; one that is purely *shi* without Stomach Qi indicates death. The winter pulse takes Stomach Qi as its foundation.
The Stomach is the sea of water and grain, governing nourishment. The pulses of all four seasons take Stomach Qi as their foundation. This is the key principle for understanding seasonal variations in disease and determining life and death.
The Spleen resides in the central region. Its healthy state is imperceptible; it is only seen when declining. If the pulse arrives like a sparrow pecking or like water dripping from a leak, this manifests as Spleen decline.