JOHN Caius, of whose name there were at least nine other forms (Cais, Cayus, Kaius, Kees, Keis, Kesse, Keys, Keyse, Keysse), was never a Regius Professor; but as the third founder in 1557 of the college which bears his name and in Fuller's words has been “a numerous nursery of eminent physicians”, as President of the Royal College of Physicians of London for nine years in all, the pioneer of practical human anatomy in this country, and in Gesner's words “the most learned physician of his age”, he was an outstanding figure in the history of the Medical School of Cambridge.

He was born at Norwich, probably in the parish of St Ethelred, on October 6, 1510, the son of Robert Caius (obiit 1532), a Yorkshireman, and Alice Wode or Woda, and after school education in his native town entered Gonville Hall on September 12, 1529, at the rather mature age, for that time, of nineteen. He was a scholar from Michaelmas 1530 to Lady Day 1533, and graduated B.A. in January 1532–3, being first in the Ordo Senioritatis, the equivalent of senior wrangler. On November 12, 1533, he was appointed the sixteenth warden or Principal of Physwick's Hostel, an annexe of the college, bequeathed in 1393 by William Physwick, Esquire Bedell (1360) of the University. On December 6, 1533, Caius was elected to a fellowship at Gonville Hall, which he retained until Michaelmas 1545.