Chapter seventy-four of the Great Treatise on the Essence of the Utmost Truth zhizhen yaodalun of the Inner Classic of the Yellow Emperor huangdi neijing records the most encompassing and original rules in Chinese medicine pathology. The nineteen patterns, most commonly known as the Nineteen Lines on Pathology, are considered to be the most authoritative instructions on classical etio-pathology and the only discourse where a differentiation method based on the five phase energetics is presented.