The Ayurvedic medical system relies heavily on a pair of texts that are revered as statements of all the fundamental principles within the tradition. The two dominant texts are the Charaka Samhita (already described) and the Susruta Samhita, both estimated to have been written around 100 A.D. These are huge volumes (an English translation of the two Indian texts runs 2,700 pages). The Susruta, though it contains a diversity of information, is mostly known as a text on surgery. The Charaka, by contrast, is relied upon as the primary source for information about basic Ayurvedic theory and about herbal medicine. Therefore, it is the quoted source book for virtually any discussion of Indian herbs.
A 5-volume translation of the Charaka Samhita, revised for publication in 1996, is available from India (a 6-volume set is also produced). Quotes from the Charaka are to be found in virtually every Ayurvedic book and article, but few practitioners outside of India go back to the original work to study the principles. There is a third Indian text that is usually grouped with Charaka and Susruta, called Vagbhata Samhita; however, this one is relatively infrequently referenced, because, according to Kutumbiah, "the object of the author was to gather up into a harmonious whole the more or less conflicting medical systems current in his time, especially those contained in the compendia of Charaka and Susruta." As such, this text is often seen as a source for academic checking of the two more famous texts, rather than having much influence as an independent work.
Kutumbiah sums up the situation regarding traditional medical texts in India this way: "The creative period of ancient Indian medicine ends with the samhitas of Charaka and Susruta. Charaka accomplished the final synthesis of Indian medicine, and Susruta that of surgery. Their works have thereafter held undisputed sway in Indian medicine up to the present time. The Indian medical writers after Charaka and Susruta were only their imitators and abstractors. No real original work was accomplished after them."
The Charaka presents steps to take in one's daily life to promote health; it also describes causes of disease (such as environmental, dietary, and emotional factors), has many chapters devoted to specific diseases with some details of disease progression, and offers a variety therapeutic measures. The Charaka mainly presents herbs, oil massages, and enemas. The heavy reliance on therapeutic massage with specific oils according to the disorder being treated and on enemas (usually made with an oil base) is unique to the Ayurvedic system.
Ayurvedic medicine has had a limited tradition of Materia Medica works (listing of herbs and their properties). In 1908, Dr. K. M. Nadkarni published a two-volume Indian Materia Medica, a guide to Ayurveda that is still considered the standard text. It combines information from ancient traditional practices, current Ayurvedic practices, and reports from Europeans (such as analysis of active constituents, pharmacology, and European uses of the same herbs). This Indian text has several limitations: it makes no reference to previous works on Indian herbs, does not outline any history of the development of the drugs, and does not indicate when an herb was introduced into practice. It provides occasional references to Charaka, but doesn't otherwise quote earlier authors on Ayurvedic medicine, except for those working right around the time of its publication, mainly R.N. Chopra.