Jean-Louis, an eminent French surgeon, was born in Paris in March 1674. His love for his favourite science was early in action. When a mere child he began of his own accord to attend the lectures of Littre, the anatomical professor; not long afterwards he was surprised one day in a granary in the act of dissecting a rabbit; and at the age of twelve he had made such progress in his class, that he was entrusted with the care of the anatomical theatre. This precocious boyhood was the prelude to a manhood of great professional eminence. After practising for eight years with marked ability in the army, he returned to Paris in 1700, and took a high position as a promoter of surgical science. His Traité sur les Maladies des Os, published in 1705, originated a new branch of pathology. His appointment to the office of lecturer in the School of Surgery in 1724, and to the directorship of the Royal Academy of Surgery in 1731, inaugurated and established a new system of surgical instruction. His numerous pupils, also, carried his principles to the most remote countries. He died in 1750, the most famous surgeon in Europe. An extensive work on surgery, which Petit left unfinished, was completed and published by Dr Lesné, under the title of Traité sur les Maladies Chirurgicales, Paris, 1774. His other productions are contained in the Memoirs of the Academy of Surgery, and in those of the Academy of Sciences.

Pierre, a French mathematician, was born at Montluçon in 1594, and removed from his native place to Paris in 1633. His aptitude for the exact sciences soon opened up for him a career of distinction. The French government employed him to inspect the seaports of France and Italy, and appointed him provincial commissary of artillery and intendant-general of fortifications. Several scientific works in the meanwhile proceeded from his pen, and increased his reputation as a man of learning. He was also honoured to take part in the celebrated discussions touching the "Dioptrics" of Descartes, and to assist Pascal in making experiments on the phenomena of the common pump. The death of Petit took place at Lagny, on the Marne, in 1677. The following is a list of the most important works of Petit: L'Usage du Compas de Proportion, 8vo, Paris, 1634; Observations touchant le Vide, 4to, Paris, 1647; Dissertation sur la Nature des Comètes, 4to, Paris, 1665; and Dissertation sur la Nature du Chaud et du Froid, 12mo, Paris, 1671.