Francis Buchanan served as a surgeon to Lord Wellesley, who was the Governor-General of India during a crucial period in the late 18th and early 19th centuries. This was a time of significant political, social, and medical transformations in India, and Buchanan played an important role in documenting various aspects of the subcontinent. Lord Wellesley served as Governor-General from 1798 to 1805 and was known for his efforts to consolidate British control in India.

So, the correct option is [2].