The treatise On Ancient Medicine () is perhaps the most intriguing and compelling work of the Hippocratic Corpus. The Corpus itself is a collection of about sixty writings covering all areas of medical thought and practice. Traditionally associated with Hippocrates, (c. 460 BC – c. 370 BC) the father of Western medicine, philological evidence now suggests that it was written over a period of several centuries and stylistically seems to indicate that it was the product of many authors dating from about 450–400 B.C. Hippocratic Corpus: structure On the basis of its diverse arguments regarding the nature of medical therapeutics, the Hippocratic Corpus could be divided into four divisions or groups. Group I: The humoral theory of medicine proposed that our bodies were made up of diverse fluids, elements, or powers, that were considered to be the basic units or fundamental building blocks of all nature. Whereas, a more simplified and categorized version of this theory is usually associated with the four humors of black bile, blood, phlegm and yellow bile, the humoral theory as presented in Group I of the Hippocratic Corpus is never structured or schematized. Its approach to understanding the diverse cause of illnesses and their cures is empirical in nature. It therefore, takes a more holistic view of the human organism which defines simple categorization of disease causality and treatment or cure. It places emphasis on physis (nature) or unitary vital force of the organism by which the physician must be guided. It is the self-healing powers of the human organism, the inner physician, which must always be consulted in the diagnosis and treatment of sickness. The interaction of the humors within man must always be seen in this light. Indeed, this group viewed the human organism as being composed of an infinite number of humors and that disease consists in the isolation of one of these humors within the organism leading to an imbalance which must be cured through coction of this humor, a process leading to the restoration of balance. Group II: The proponents of this group argue that in addition to cure through coction and evacuation may be added the therapeutic approach of treatment of sickness through the administration of contraries. This could be in the form of dietary prescription but also medicinal substances. Medicinal substances are chosen on the basis of their indwelling powers or virtues, a method of analysis also applied