At the foundation of Human Health is Digestion, and correct Digestion depends on the intake of the nutrition suitable for the constitution, season and age.

From Digestion comes two channels of Nutrition: a more physical nutrition which is bound to the Blood and is composed of Humors. The second is more ethereal or Spiritual, and was termed the Three Spirits in Western Physiology, and is closely allied to the Three Treasures (San Bao) of TCM. The Three Spirits are Natural Spirit (Essence of Food), Vital Spirit (Qi) and Animal Spirit (Shen). The best Essence of Food taken forms Natural Spirit, the denser parts forming the Four Humors (Blood, Bile, Phlegm and Melancholy). The best Essence of Food (Natural Spirit) travels with the Blood to the Heart where it mixes with the best essence of Air inspired to form Vital Spirit (Qi). The best Essence of Vital Spirit forms Animal Spirit (Shen, or Spirit proper) in the Brain. This is called Animal Spirit because it is only found in Animals and is responsible for Consciousness.

This diagram illustrates the Physiology envisioned by Galen. Food is digested in the Stomach, Chyle is absorbed by the Portal Vein and carried to the Liver to form the 4 Humors and Natural Spirit, the Best Essence of Food ingested.

Natural Spirit passes to the Heart to be infused with Air in the Lungs, this fusion forming Vital Spirit, or Qi. The finest part of Vital Spirit forms Animal Spirit (Spirit) in the Brain


Galens Physiology-Greek Biology and Medicine-Singer-1922

Ayurveda recognises 7 Bodily Constituents or Tissues. This effectively represents Digestion, from Chyle, to Blood, to the formations of Muscles, Tendons, Bones and Marrow, eventually leading to formation of Sperm. The remainder becomes Essence. This effectively represents the end result of First, Second, and Third Digestion in the Galenic system.


In the following diagram, the Four Elements, Three Spirits (Three Treasures of TCM) and 7 Tissues of Ayurveda are all comprehended into one understanding.