问曰∶舌黑而润，何以是直中寒证？答曰∶黑者，北方水色也，黑而且润，则知其为寒
证矣。若传经热邪，舌苔先黄而后黑，必干燥而无津液，此火极似水之象，譬如燔柴变炭之
意，乃热甚也。若舌黑而润，津液如常，乃寒气乘心，北方之水色见也，宜急温之。故曰舌
黑而润，为直中寒证也。
问曰∶脉沉细无力，何以是直中寒证？答曰∶脉者，阳气主之也，气盛则脉旺，气弱则
脉细。今脉沉细无力，则为中寒无疑矣。又问曰∶经云∶诸紧为寒，何也？答曰∶紧者，脉
如引绳转索，有风起水涌之象，北方刚劲之气也，与数脉不同。数以至数名，紧以形象论也
经云∶诸紧为寒。寒之诊不一，紧为寒，沉细无力亦为寒，迟为寒，又脉洪大搏指，按之
空虚者，亦为寒。譬如数则为热，洪大为热，沉实有力为热，脉涩滞，郁而不通者，亦为热
全在以证互相参考，时而舍脉从证，时而舍证从脉，活活泼泼不胶己见。其于诊法庶矣乎
问曰∶吐蛔何以是直中寒证？答曰∶病患胃寒食少，蛔泛上隔，闻食臭而出，故吐蛔也
宜用理中安蛔散以温之，不可轻用凉药。又问曰∶阳证亦有吐蛔者，何也？答曰∶病久胃
空，既无谷气，蛔上隔求食，至咽而出，须看兼证如何，若阳黄发斑，口疮咽燥，大渴消水
或用清剂，可以收功。然而寒证吐蛔者多，热证吐蛔者少，最宜斟酌。
问：舌色发黑且湿润，为什么这是寒邪直中脏腑的证候？
答：黑色是北方水的颜色，舌黑而且湿润，就可以知道这是寒证。如果是传经的热邪，舌苔会先变黄然后变黑，必定干燥而没有津液，这是火极似水的现象，就像燃烧柴草变成木炭的意思，属于热盛的表现。如果舌黑而湿润，津液如常，这是寒气侵犯心脏，显示出北方水的颜色，应当紧急温补。所以说舌黑而润，是寒邪直中的证候。
问：脉象沉细无力，为什么这是寒邪直中脏腑的证候？
答：脉象是由阳气主导的，气盛则脉象旺盛，气弱则脉象细弱。现在脉象沉细无力，那么就是中寒无疑了。又问：经典说“各种紧脉都是寒证”，为什么呢？
答：紧脉，脉象像拉紧的绳子或扭转的绳索，有风起水涌的景象，这是北方刚劲之气，与数脉不同。数脉是以至数（频率）来命名的，紧脉是以形象来论述的。经典说：“各种紧脉都是寒证。”寒证的诊法不止一种，紧脉为寒，沉细无力也为寒，迟脉为寒，还有脉象洪大搏指，但按之空虚的，也是寒证。例如数脉则为热，洪大为热，沉实有力为热，脉象涩滞、郁结不通的，也是热证。全在于以症状互相参考，有时舍脉从证，有时舍证从脉，灵活变通而不固执己见。这样对于诊法就差不多精通了。
问：吐蛔虫为什么是寒邪直中脏腑的证候？
答：病人胃寒食少，蛔虫泛溢上膈，闻到食物的气味就出来，所以吐蛔虫。应当使用理中安蛔散来温中，不可轻易使用凉药。又问：阳证也有吐蛔虫的，为什么呢？
答：病久胃空，既没有谷气，蛔虫上膈寻找食物，到了咽喉而出，必须看兼夹的症状如何，如果有阳黄、发斑、口疮咽燥、大渴饮水等症状，可以使用清热剂，可以取得疗效。然而寒证吐蛔的多，热证吐蛔的少，最宜仔细斟酌。
Q: Why is a black and moist tongue indicative of direct invasion by cold pathogen (Zhi Zhong Han Zheng)?
A: Black is the color of Water in the North. If the tongue is black and moist, it indicates a Cold syndrome. If heat pathogen transmitted through the meridians, the tongue coating would first turn yellow and then black, and must be dry without fluids; this is the phenomenon of extreme Fire resembling Water, similar to the idea of firewood turning into charcoal due to intense heat. However, if the tongue is black and moist with normal fluids, it indicates Cold pathogen invading the Heart, manifesting the color of Northern Water. Urgent warming treatment is required. Therefore, a black and moist tongue is a sign of direct invasion by cold pathogen.
Q: Why is a deep, fine, and forceless pulse indicative of direct invasion by cold pathogen?
A: The pulse is governed by Yang Qi. When Qi is abundant, the pulse is vigorous; when Qi is weak, the pulse is fine. A deep, fine, and forceless pulse undoubtedly indicates internal Cold. Another question: The classics state that "all tight pulses indicate Cold." Why?
A: A tight pulse feels like a drawn rope or twisted cord, resembling wind rising and water surging; it represents the rigid Qi of the North, which differs from a rapid pulse. A rapid pulse is defined by its frequency (number of beats), whereas a tight pulse is defined by its morphology. The classics state: "All tight pulses indicate Cold." There are various diagnoses for Cold: a tight pulse indicates Cold, a deep and fine forceless pulse indicates Cold, a slow pulse indicates Cold, and even a洪大 (Hong Da / Surging) pulse that beats forcefully against the finger but feels empty upon pressure also indicates Cold. Conversely, a rapid pulse indicates Heat, a surging pulse indicates Heat, a deep, solid, and forceful pulse indicates Heat, and a choppy, stagnant, and obstructed pulse also indicates Heat. One must refer to symptoms mutually; sometimes discard the pulse in favor of symptoms, sometimes discard symptoms in favor of the pulse, remaining flexible and not adhering rigidly to personal views. In this way, one is nearly proficient in diagnostic methods.
Q: Why is vomiting roundworms indicative of direct invasion by cold pathogen?
A: When a patient has Stomach Cold and poor appetite, roundworms may overflow upwards to the diaphragm. Upon smelling food odor, they emerge, causing vomiting of roundworms. One should use Lizhong Anhui San (Regulate the Middle Decoction to Pacify Roundworms) to warm the interior; cool medicines should not be used lightly. Another question: Are there cases of vomiting roundworms in Yang syndromes?
A: After prolonged illness, the Stomach becomes empty lacking Gu Qi (Grain Qi). Roundworms ascend to the diaphragm seeking food and emerge at the throat. One must examine accompanying symptoms. If there are Yang Jaundice, macules, mouth ulcers, dry throat, and excessive thirst for water, cooling agents can be used to achieve success. However, vomiting roundworms is more common in Cold syndromes than in Heat syndromes, so careful deliberation is essential.