Cauliac Chailiac, or Chaulieu, Gui de, a French surgeon of the 14th century, studied at Mont-pellier and Bologna, practised his profession in Lyons, and was afterward employed by three popes of Avignon, Clement VI., Innocent VI., and Urban V. He is the author of a remarkable treatise on surgery, entitled Inventarium, sive Collectorium Partis Chirurgicalis Medicinae, which was translated into French by Laurent Joubert, under the title of Grande chirurgie, and accompanied with annotations and an index by his son Isaac Joubert (8vo, Lyons, 1592). This was the first work of importance on the principles and practice of surgery published in Europe after the middle ages, and during two centuries it was considered the classical work on that branch of science. It is even now esteemed for its simplicity and clearness on many points. Plasters and poultices, ointments and embrocations were almost the only resources of surgical practice in western Europe before the time of Chauliac. He reestablished the practice of such operations as had been described and performed by the ancient Greeks and the Arabian surgeons, invented several new instruments, and undertook certain operations on the crystalline lens, for the restoration of sight, in cases of cataract.

He laid the foundations of the modern principles and practice of surgery; and though his works are tinged with astrological notions, they are replete with practical instruction. He also wrote a description of the plague which visited France in 1348, and by which he was himself attacked.