Constantinus Varolius, whose name is imperishably connected with that part of the brain which is known as the “Pons Varolii,” was born in Bologna in 1543. He was appointed Professor of Anatomy in the Academy of his native city at an early age, and soon distinguished himself by the careful studies which he made of the human brain and nervous system in general. Before his untimely death at the age of thirty-two he was chosen the attending physician of Pope Gregory the Thirteenth. His earliest published work bears the title “_De nervis opticis, etc., epistola_,” Padua, 1573. Volcher Koyter, who was born at Groningen, North Holland, in 1534, studied under Fallopius and Guillaume Rondelet (1507–1566), to whom the University of Montpellier was indebted for its anatomical theatre, and to whom (rather than to Gaspard Bauhin of Basel) is due the honor of discovering the ileo-caecal valve. Koyter was one of the earliest workers in the field of comparative anatomy--a department of knowledge to which Vesalius had already made some creditable additions; and his two most important published treatises bear these titles: “_De ossibus et cartilaginibus corporis humani tabulae_” (Bologna, 1566), and “_Externarum et internarum principalium humani corporis partium tabulae_” (Nuremberg, 1573). He died in 1600. Hieronymus Fabricius was born in 1537 at Acquapendente, a small city of Etruria, about fifty miles northwest of Rome. He studied anatomy at Padua under Fallopius, and, after the latter’s death, was assigned to the duty of making the necessary dissections and anatomical demonstrations before the class. In 1565 he was appointed Professor of Surgery, with the understanding that he was to continue giving his demonstrations in anatomy. The salary which he received for this double work was 100 ducats, but it was increased from time to time until finally he was paid 1100 ducats yearly. At the end of thirty-six years he was retired upon a pension of 1000 ducats for the remainder of his life, and was allowed the privilege of appointing his successor in the Chair of Surgery. He gave the place to Julius Casserius in 1609. To distinguish him from another Fabricius, who gained great distinction in the field of surgery, it has always been customary for later historical writers to speak of him as “Fabricius ab Acquapendente.” His namesake is known as “Fabricius Hildanus.”