While Mercurialis was teaching medicine, he had as a student Johannis Chrosczieyoioskii, of whom nothing is known except that he made copious notes and wrote "de Morbis Puerorum." As the title page states, it is a "tract on children's diseases, very complete and filled with various learning, very useful not only to Doctors, but also to Philosophers; carefully taken down from the mouth of the Most Honorable Geronimo Mercuriali of Forli, the famous Doctor, and digested into three books."
Mercurialis was born at Forli. He studied medicine for some years in Bologna and received his doctor's degree at Padua, after which he practiced at Forli. His fellow townsmen chose him as their representative on a political mission to Rome, where Cardinal Farnese induced him, doubtless without difficulty, to stay. The next seven years were spent in studying the ancient and medieval writers when he was called to the vacant chair