Based on the study of a medical course taught at the Faculty of Medicine in Paris by Jean Riolan in 1584-1585 and kept at the Carnegie Library in Reims, this article presents syphilis, called "Indian disease", as an illness with a new clinical description. The professor studies its origin, its symptoms, its cure with a decoction of gaiac wood which is inefficient, and a cure with quicksilver under different forms (pills, unctions, fumigations) which is more reliable. It gives an example of the adaptation of a much-disparaged medicine to a disease with symptoms unknown from ancient authors.