According to the philosophical concepts on which Ayurveda is based, all bodies – material, living, conscious and unconscious – are evolved out of Prakrti (the ultimate ground) by the subtle influence of the Purusa, the absolute or the primal self conscious principle and every component of the human organism is created out of the tattvas (fundamental compounds) as evolved out of the Prakrti. When all the eleven indriyas (mind, the five sense organs and the five organs of motion and action), the three dosas (the air, radiant energy and water), the agni (digestive fire), the malas (excretions), the kriyas (like sleep, elimination, respiratory, etc.) and the seven dhatus (elementary stuff) are in normal state and in equilibrium then the health is in an ideal state. The main aims of Ayurveda include maintenance of this equilibrium, and its repair in case of any imbalance and derangement. Ayurveda attempts this process by the application of all spiritual and material resources available to man.
The earliest-recorded knowledge about Ayurveda is found in the Rigveda and the Atharvaveda, both of the second millennium BC. The Atreya Samhita is perhaps the oldest medical book in the world; it survives from Taksashila University, going back to the mid-I Millennium BC. The Atharvaveda lists eight divisions of Ayurveda: internal medicine, surgery of head and neck, ophthalmology, surgery, toxicology, psychiatry, paediatrics, gerontology or science of rejuvenation and the science of fertility. At about 500 BC in the University of Banaras, Susruta, a surgeon, who developed the operative techniques of rhinoplasty (plastic surgery), wrote the Susruta Samhita, which describes a highly developed surgery. The physician Caraka revised and supplemented the Atreya Samhita; his book, the Carak Samhita is a vast work on internal medicine.
Susruta Samhita: According to Susruta Samhita the purpose of Ayurveda is not only to cure illness and affliction but also to preserve health and ensure a long happy life. Susruta Samhita deals specially with the therapeutic branch of Ayurveda. It contains one hundred and twenty chapters, distributed in five divisions: Sutrasthana (fundamental postulates cover 46 chapters), Nidanasthana (pathology, covers 16 chapters), Sarirasthana (embryology and anatomy cover 10 chapters), Cikitsasthana (medical treatment covers 40 chapters), Kalpasthana (toxicology covers 8 chapters) and Uttaratantra (specialized knowledge covers 66 chapters) respectively.
Caraka Samhita: Caraka Samhita is an exhaustive work on medicine. It is said that Caraka’s original was the Samhita of Agnivesa, a disciple of the medical sage Atreya. Long passages in the Caraka Samhita are in the form of questions and answers between Atreya and Agnivesa. Caraka is a class title of a school of physicians, existing from Vedic times and also the personal title of a physician in the court of King Kaniska. (There is no unanimity about Caraka’s date yet). The subject matter of the Caraka Samhita has been divided into 8 sections and 120 chapters. The total number of chapters (120) probably refers to the maximum life span (120 years) of man because the ultimate object of treatise is to promote longevity