This is primarily a collection of letters and manuscripts sent to Wistar by prominent men who were among his many correspondents. These documents reflect his broad interests, including botany, paleontology, medicine, the American Philosophical Society, and André Michaux's plans for exploring the Missouri.

Fothergill writes to an English physician, J. Woodforde, from Bath and Bristol in England and from Philadelphia. The letters concern their common interests in medicine, with comments on current events, American and Philadelphia society, and medicine in the United States.