ABERNETHY, JOHN (1764-1831), British surgeon, was born in London on April 3 1764. He was apprenticed in 1779 to Sir Charles Blicke, then assistant surgeon to St. Bartholomew's Hospital, and studied under Sir William Buzard at the London Hospital and under John Hunter. When Blicke became surgeon to the hospital, Abernethy became assistant surgeon. He began to lecture to students in his house. The lectures were so crowded that the governors of the hospital decided to build a regular lec ture theatre. Abernethy's best known work is Surgical observa tions on the constitutional Origin and Treatment of Local Dis eases (1809). He had enjoyed great celebrity in private practice, enhanced, it is said, by his rough manners. He was surgeon to the hospital 1815-27, and died at Enfield April 20 1831.
A collected edition of his works was published in 183o. A biography, Memoirs of John Abernethy, by George Macilwain, appeared in 1853. ABERRATION IN OPTICAL SYSTEMS, the deviation of light rays from certain points through which they should pass in order to satisfy the conditions necessary for distinct focus. Spherical aberration results in distortion of the image, and chro matic aberration produces coloured fringes around an otherwise white image. (See OPTICS ; PHOTOGRAPHY : Apparatus.)