As Horsley’s workload increased at the National Hospital, it became necessary to make new surgical appointments to support him. Charles Ballance (1856–1936) came on staff in 1891 but was somewhat overshadowed by Horsley – whom he had assisted in the famous operation on Captain Gilbey (discussed in Chapter 5) – and resigned in 1908. He became a celebrated aural and general surgeon in his own right. Donald Armour (1869–1933) and the technically brilliant Percy (“Pretty Percy”) Sargent (1873–1933) both assisted Horsley in the early years of the twentieth century, became assistant surgeons at the hospital in 1906, and full surgeons three years later, after Ballance had resigned. All three made their mark in the field of surgical neurology, helping to establish the tradition of neurosurgical excellence at the hospital. But it was Horsley more than anyone who was responsible for advancing the emerging specialty of neurosurgery and who developed a school of followers that included Wilfred Trotter (p. 00), Armour, and Sargent in Britain, Ernest Sachs (p. 00) in the United States, Edward Archibald in Canada, Thierry de Martel in France, and Vilhelm Magnus in Norway.