Po is the Animal Soul. Po is completely tied to time and space. It is about momentary reactions. It is the reactivity and animation of the person. It is strongly tied to the seven emotions. It is unthinking and compelling passion. Po is the part of Shen that takes in what the five physical senses, especially touch. Po is the animal wit, embodied knowing, receptivity, and appreciation
The seven emotions of Traditional Chinese Medicine are Joy, Fright, Worry, Sadness, Grief, Fear, and Anger. These all manifest in Po. Too much of any of these emotions cause imbalances, which cause health problems.
The symbol for Po is made up of two symbols, meaning White and Demon. The word for Demon can also be translated as Ghost. So Po is the white demon, or white ghost.
Po is Yin to Hun's Yang. Po is the lowest part of Shen, closest to the body. Some Taoist branches believe that each person has seven Po and three Hun. This is based on the nine palace magic square.
Traditional Chinese Medicine teaches Po ceases to exist when a person dies. Taoism and other Chinese religions and folk beliefs, however, teach that it sinks into the earth if burried properly, or becomes a kuei, a ghost, if not properly burried or not receiving the proper rites.
Po is associated with the element Metal, and hence is centered in the Lung. This makes sense, since Po provides life, just as the breath in the Lungs brings life. Po is associated with the West and Tiger. The Tiger represents dignity, ferocity, sterness, courage, and protection. It also represents power, energy, royalty, generosity, illumination, and unpredictability. This gives some clues on what Po is like.
Po has two virtues, or two aspects to its virtue. First is justice, being impartial, deliberate, and fair. Second is preciousness, being perfection and completeness in the moment, grasping the overflowing fullness of a momentary flash of insiration, or the profound awe and eternity in a single work of great art.
If you correlate the five Shen with the five souls in Kabbalah, Po is obviously the Nefesh (Fetch in Feri). The Nefesh is the part of the body most closely tied to the body. It is connected to the five senses. It is the instincts (and emotions in Feri), the unthinking and compellign passion. It animates the body and is our reactions. The Nefesh is the soul that appreciates beauty, loves art.
If you look at the following link, it describes ways to feed and help Po be healthy. If you read them, you will noticed that they are the same things Feri teaches as being the things to do for the Fetch.
The po represent the yin, materialized aspect of the soul. FFF
~Muninn's Kiss