Appetite and wrath are desiderative faculties of the soul. But wrath and appetite are different. And one could ask: "how"?, "why"? Does not the wrathful person have an appetite for vexing in return the one who caused pain before? But what else? Does not reason also have an appetite for knowledge and theoretical matters? In addition, we say that appetite is so called both in a general and in a more specific way. Just as the disposition is both generally so called in reference to a state, and the disposition is also specifically so called which is opposed to the state, so too appetite is generally so called in reference to all the faculties of the soul, and the opposed disposition is also so called more specifically with respect to wrath.
But the one who defines wrath as "a desire for vexing in return" defined it not according to its nature but dialectically. For he did not show the essence of wrath but, in dividing, he defined that from which, in the essence of wrath, it has its being -- from which we could not define the attributes of wrath, just as when one says that anger is an effervescence of the blood around the heart produced by the desire for vexing in return. For thus he makes the attributes known. And this is so because a certain palpitation of the heart follows closely on those who become angry, and because heat arises around those parts, since the angry people turn red. And this is produced by the movement of the blood.
The affections of the soul, which belong to both parts, cannot be separated even conceptually.
For wrath exists in reason, in breathing, and in the living body. For example, reason entrusts the desire to the breathing, the breathing with the desire sets in motion the blood around the heart of the animal, just as it occurs with a king, a general, and an army. For the king entrusts the general with defending [us] from certain people, and the general sets in motion his soldiers, and these defend [us]. Now the wrath that exists in reason is not separable from the animal (for such a wrath is separable from any body). But the wrath which exists in breathing, even if it is not entirely separable, yet it is separable from an earthy body. And the third [kind of wrath], i.e. the seething of the blood around the heart, is inseparable from the living body.