WHILE THE SOUL-POWER IS EVERYWHERE, THE PRINCIPLE OF ACTION IS LOCALIZED IN THE SPECIAL ORGAN.
23. Since, for the body, being animated amounts to being penetrated by the light shed by the soul, every part of the body participates therein in some particular manner. Each organ, according to its fitness, receives the power suitable to the function it fulfils. Thus we may say that the power of sight resides in the eyes; that of hearing in the ears; that of taste in the tongue; that of smell in the nose; that of touch in the whole body, since, for the latter sense, the whole body is the organ of the soul. Now as the instruments for touch are the first nerves, which also possess the power of moving the organism, as they are the seat of this power; as, besides, the nerves originate in the brain, in the brain has been localized the principle of sensation and appetite — in short, the principle of the whole organism; no doubt because it was thought that the power which uses the organs is present in that part of the body where are the origins of these organs. It would have been better to say that it is the action of the power that makes use of the organs that originates in the brain; for that part of the body from which starts the movement impressed on the organ had to serve somewhat as a foundation for the power of the workman, a power whose nature is in harmony with that of the organ (it sets in motion); or rather, this part of the body does not serve as foundation for this power, for this power is everywhere, but the principle of the action is in that part of the body in which is the very principle of that organ.
REASON IS IN THE HEAD, BUT NOT IN THE BRAIN, WHICH IS THE SEAT OF THE INTERMEDIARY, THE POWER OF SENSATION.
On the other hand, as the power of sensation and the power of appetite, which belong to the sensible and imaginative soul, are beneath reason, because they are related to what is inferior, while reason is above, the result was that the ancients localized reason in the highest part of the animal, in the head; not that reason is in the brain, but because reason is seated in the sense-power, by the intermediation of which, only, reason may be said to reside in the brain. The sense-power, surely, had to be attributed to the body, and, within the body, to the organs most capable of lending themselves to its action. Reason, which has no (direct) dealing with the body, had however to be in relation with the sense-power, which is a form of the soul, and can participate in reason. The sense-power, does, to a certain extent, judge; and the power of imagination has something intellectual. Last, the appetite, and the desire somehow connect with imagination and reason. Reason, therefore, is in the head, not as in a locality, but because it is in relation with the sense-power which resides in that organ, as has been shown above.
GROWTH IS LOCALIZED IN THE LIVER, ANGER IN THE HEART.
As the power of growth, nutrition, and generation operates all through the entire body; and as it is by the blood that the body is nourished; as the blood is contained in the veins; and as the veins, as well as the blood, originate in the liver; this organ has been assigned as the seat of that part of the soul called appetite; for appetite is involved in the power of begetting, of feeding and increasing the body. Further as the blood (purified by respiration) is subtle, light, mobile and pure, the heart becomes a suitable instrument for the power of anger, for the blood that possesses these qualities starts from the heart. Therefore, with good reason, the heart is assigned as the seat of the turbulent convulsions of the power of anger.