夫痘全诊乎形色，谓之形者，痘之形也，凡始初之形，尖圆坚浓，起壮之形，发
荣滋长，成浆之形，饱满充盈，收靥之形，敛束完固与水珠光泽者皆正形也。或平或
陷，形之变也，是以初出之时隐若蚊蚤之迹，空若蚕种之脱，薄如麸片，密如针头，
如热之痱，寒之粟者，必不能起发而死。若粘聚模糊，肌肉虚浮，溶软嫩薄，皮肤溃烂
者必不能收靥而死。谓之色者，痘之色也。喜鲜明而恶昏暗，喜润泽而恶干枯，喜苍蜡
而恶娇嫩，红不欲艳，艳则宜破，白不欲灰，灰则难靥，由红而自，白而黄，黄而黑
者，此终始次递渐变之正色也。若出形而带紫，起发而灰白色之变也。更有根窠脚地，
四者难名立各殊，总不离乎形色二字，诚为不易之要法，何谓窠？中透而起顶者是也。
何谓根？外圈而红者是也，然圈之红否则中之虚实，与痘毒之浅深，可见矣。窠之起否
则根之浅深，与气血之盈亏，可定矣。所谓脚地者，亦本乎根窠之圆混，痘粒之疏密
也。夫红晕之处谓之脚，凡彼此颗粒界线分明，不散不杂者，此痘脚明净也，若空隙之
处，便谓之地，凡彼此颗粒不相连缀者，此地面明净也，总之根欲其活，窠欲其起，脚
欲其固，地欲其宽，四者俱顺痘虽重而无虑也。然圆者气之形也。气盛则痘窠圆满而周
净。晕者血之形也，气盛则必痘窠光明而红活，故气虚则顶陷，气散则窠塌，然有气虚
极而不塌陷者，乃火载之，是以虽见圆满，实空壳如泡然也。抑气虚则晕淡，血惫则晕
枯，然有血虚极而外面犹红者，乃火上浮，是以虽见圆晕，实枯槁不润泽也。形色者，
乃气血之标，气血者，乃形色之本也。诀曰∶有盘有顶终须贵，有顶无盘却不宜。观
此二语，顶固俱属痘家之紧要，而盘实更重于顶也。盘者，即根脚之义也。顶者，即充
足之象也。总而言之，痘疮之始终，咸赖乎气血，即根脚亦必籍气血以承载，充足亦必
资气血以营运，以形色较之，宁可形平地而色红活，不可形尖圆而色晦滞，所谓宁教有
色无形，休教有形无色，盖充足者由乎气，气可旺于斯须也。根脚者即华于血，又赖气
以拘之，气血兮，德而成，且补血难图捷效，故更重之也。
痘疮的诊断完全依赖于观察其“形”与“色”。所谓“形”，是指痘疮的形态。凡是初起时的形态，如尖圆、坚实、浓密；起发时的形态，如隆起、繁荣、滋长；成浆时的形态，如饱满、充盈；收靥（结痂脱落）时的形态，如收敛束固、如水珠般光泽，这些都是正常的形态。如果平坦或凹陷，则是形态的变异。因此，在刚发出时，若隐约像蚊蚤叮咬的痕迹，空洞像蚕种蜕皮，薄如麸片，密如针头，或者像热天起的痱子、受寒起的粟粒疹，必然不能起发而死亡。如果粘连聚集成团、模糊不清，肌肉虚浮，松软嫩薄，皮肤溃烂的，必然不能收靥而死亡。
所谓“色”，是指痘疮的颜色。喜欢鲜明而厌恶昏暗，喜欢润泽而厌恶干枯，喜欢苍老蜡质样而厌恶娇嫩，红色不追求艳丽，艳丽则容易破溃，白色不追求灰暗，灰暗则难以结痂。由红变白，由白变黄，由黄变黑，这是从头到尾依次递进变化的正常颜色。如果出形时带紫色，起发时呈灰白色，则是颜色的变异。更有根窠（痘疮底部的红晕范围）、脚地（痘疮之间的空隙），这四个方面难以用言语一一列举，但总离不开“形色”二字，这确实是不可改变的重要法则。
什么叫“窠”？中间透亮且顶起的是窠。什么叫“根”？外圈发红的是根。然而，看圈的红色与否，就可以知道中间的虚实以及痘毒的浅深。看窠是否起发，就可以确定根的浅深以及气血的盈亏。所谓“脚地”，也是基于根窠的圆润浑厚和痘粒的疏密而言。凡是有红晕的地方称为“脚”，凡是彼此颗粒界线分明，不散乱不混杂的，这叫痘脚明净。凡是空隙的地方称为“地”，凡是彼此颗粒不相连缀的，这叫地面明净。总之，根要活络，窠要起发，脚要稳固，地要宽阔，这四点都顺遂，痘疮虽然严重也不必担忧。
圆的形态是气的表现。气盛则痘窠圆满而且周围洁净。红晕是血的表现，气盛则痘窠光明而且红活。所以气虚则顶部凹陷，气散则窠塌。然而有气虚极却不塌陷的，是被火邪托举着，所以虽然看起来圆满，实际上却是空壳像水泡一样。气虚则红晕淡，血疲惫则红晕枯槁。然而有血虚极而外面仍然红的，是火邪上浮，所以虽然看到圆晕，实际上是枯槁不润泽的。“形色”是气血的外在表现，“气血”是形色根本。口诀说：“有盘有顶终须贵，有顶无盘却不宜。”观察这两句话，顶固然都是痘家紧要之处，而盘（即根脚）实际上比顶更重要。盘，就是根脚的意思。顶，就是充足的现象。总而言之，痘疮的始终，都依赖乎气血，即使根脚也必须籍助气血来承载，充足也必须依靠气血来营运。比较形色而言，宁可形状平坦而颜色红活，不可形状尖圆而颜色晦滞，这就是所谓的“宁教有色无形，休教有形无色”。因为充足是由气决定的，气可以在短时间内旺盛。根脚即华于血，又赖气来约束它，气血相辅相成，而且补血难以求得快速见效，所以更重视根脚（血/盘）。
The diagnosis of smallpox relies entirely on observing its *xing* (form) and *se* (color). By *xing* (form), we mean the shape of the pustules. Normal forms include: at the initial stage, being pointed or round, firm and dense; during the eruption phase, rising, flourishing, and growing; when forming pus, being full and plump; and during the crusting phase, being gathered and solid, with a luster like water droplets. Flatness or depression are variations of form. Therefore, if upon emergence, the lesions appear faintly like mosquito bites, hollow like shed silkworm skins, thin as bran flakes, dense like needle heads, or resembling heat rash (*Fei Zhen*, miliary rash) or cold-induced millet-like bumps, they will certainly fail to erupt and lead to death. If they adhere in clumps, are indistinct, have flaccid and floating flesh, are soft, tender, and thin, or if the skin ulcerates, they will certainly fail to crust over and lead to death.
By *se* (color), we mean the hue of the pustules. Brightness is preferred over dullness; moisture is preferred over dryness; a mature, waxy appearance is preferred over delicate tenderness. Red should not be overly brilliant, for brilliance implies a tendency to rupture; white should not be grayish, for grayness makes crusting difficult. The progression from red to white, from white to yellow, and from yellow to black represents the normal sequential transformation of colors throughout the disease course. Purple hues upon emergence or grayish-white tones during eruption indicate abnormal color changes. Furthermore, the *Ke* (nest/base), *Gen* (root), *Jiao* (foot), and *Di* (ground) are four aspects that are difficult to describe exhaustively but fundamentally revolve around "form" and "color." This is an unchanging essential method.
What is the *Ke* (nest)? It refers to the center which is translucent and raised. What is the *Gen* (root)? It refers to the outer ring which is red. Observing whether this ring is red allows one to discern the emptiness or fullness in the center and the depth of the *Du* (toxin). Whether the *Ke* rises indicates the depth of the root and the sufficiency or deficiency of *Qi* (vital energy) and *Xue* (blood). The term *Jiao Di* (foot ground) also depends on the roundness and integrity of the root/nest and the density of the pustules. Areas with red halos are called *Jiao* (foot); when individual pustules have clear boundaries without scattering or mixing, it is termed "clear foot." Empty spaces between pustules are called *Di* (ground); when pustules do not connect, it is termed "clear ground." In summary, the root should be active, the nest should rise, the foot should be firm, and the ground should be broad. If these four conditions are met, even severe smallpox need not cause concern.
Roundness is the form of *Qi*. When *Qi* is abundant, the nests are round and the surrounding area is clean. The halo is the form of *Xue*. When *Qi* is abundant, the nests are bright and the redness is lively. Thus, *Qi* deficiency leads to depressed tops, and *Qi* dispersion leads to collapsed nests. However, in cases of extreme *Qi* deficiency where there is no collapse, it is due to *Huo* (fire/toxic heat) carrying them up; thus, although they appear round, they are actually empty shells like blisters. *Qi* deficiency results in pale halos, and *Xue* exhaustion results withered halos. Yet, in cases of extreme *Xue* deficiency where the exterior remains red, it is due to *Huo* floating upward; thus, although a round halo is seen, it is actually withered and lacks moisture. *Xing* and *Se* are the manifestations of *Qi* and *Xue*, while *Qi* and *Xue* are the roots of *Xing* and *Se*. A maxim states: "Having both base and top is ultimately noble; having top but no base is inadvisable." Observing this, while the top is crucial, the base (*Pan*, synonymous with root/foot) is even more important. The base signifies the foundation, and the top signifies sufficiency. Ultimately, the entire course of smallpox depends on *Qi* and *Xue*; the base requires *Qi* and *Xue* to support it, and sufficiency requires *Qi* and *Xue* to circulate. Comparing form and color, it is better to have a flat form with lively red color than a pointed/round form with dull color. This is expressed as: "Better to have color without distinct form, than form without color." Sufficiency derives from *Qi*, which can become vigorous quickly. The base relates to *Xue* (blooming) and is constrained by *Qi*. Since *Qi* and *Xue* work together, and tonifying *Xue* rarely yields rapid effects, the base (related to blood) is emphasized further.