linguistic:paraphrasing, structural:expansion, linguistic:voice_change
Main texts

Many ancient works on ayurvedic medicine are lost to posterity, but manuscripts of three principal early texts on ayurveda have survived to the present day. These works are the Charaka Samhita, the Sushruta Samhita and the Bhela Samhita. The dating of these works is historically complicated since they each internally present themselves as composite works compiled by several editors. All past scholarship on their dating has been evaluated by Meulenbeld in volumes IA and IB of his History of Indian Medical Literature. After considering the evidence and arguments concerning the Suśrutasaṃhitā, Meulenbeld stated (IA, 348),

The Suśrutasaṃhitā is most probably the work of an unknown author who drew much of the material he incorporated in his treatise from a multiplicity of earlier sources from various periods. This may explain that many scholars yield to the temptation to recognize a number of distinct layers and, consequently, try to identify elements belonging to them. As we have seen, the identification of features thought to belong to a particular stratum is in many cases determined by preconceived ideas on the age of the strata and their supposed authors.

The dating of this work to 600 BCE was first proposed by Hoernle over a century ago, but has long since been overturned by subsequent historical research. The current consensus amongst medical historians of South Asia is that the Suśrutasaṃhitā was compiled over a period of time starting with a kernel of medical ideas from the century or two BCE and then being revised by several hands into its present form by about 500 CE. The view that the text was updated by the Buddhist scholar Nagarjuna in the 2nd century CE has been disproved, although the last chapter of the work, the Uttaratantra, was added by an unknown later author before 500 CE. Similar arguments apply to the Charaka Samhita, written by Charaka, and the Bhela Samhita, attributed to Atreya Punarvasu, that are also dated to the 6th century BCE by non-specialist scholars but are in fact, in their present form, datable to a period between the second and fifth centuries CE. The Charaka Samhita was also updated by Dridhabala during the early centuries of the Common Era.

The Bower Manuscript (dated to the early 6th century CE) includes of excerpts from the Bheda Samhita and its description of concepts in Central Asian Buddhism. In 1987, A. F. R. Hoernle identified the scribe of the medical portions of the manuscript to be a native of India using a northern variant of the Gupta script, who had migrated and become a Buddhist monk in a monastery in Kucha. The Chinese pilgrim Fa Hsien (c. 337–422 CE) wrote about the healthcare system of the Gupta empire (320–550) and described the institutional approach of Indian medicine. This is also visible in the works of Charaka, who describes hospitals and how they should be equipped.

Some dictionaries of materia medica include Astanga nighantu (8th century) by Vagbhata, Paryaya ratnamala (9th century) by Madhava, Siddhasara nighantu (9th century) by Ravi Gupta, Dravyavali (10th century), and Dravyaguna sangraha (11th century) by Chakrapani Datta, among others.