PETRUS, born at Paris, was one of the greatest surgeons of the eighteenth century. In the time of Louis XIV, he was appointed anatomical and chirurgical demonstrator in the Garden of Plants, and he was the first who held that place. He was surgeon in ordinary to Maria Theresa of Austria, queen of France, and to two dauphinesses and the royal children. He was the author of several works, both on anatomical and surgical subjects. One of the first of his publications is entitled Anatomie de l'Homme, suivant la circulation du sang, et les nouvelles découvertes, 8vo, which appeared in 1690, and has been frequently reprinted, and translated into different languages. It was translated into the Tartar dialect by a Jesuit, for the use of Kang-hi, emperor of China. This work has been considered as a useful compendium of anatomy. In another work which he published in 1698, entitled Dissertation Historique et Physique sur la Génération de l'Homme, he supports the ovarian hypothesis. In 1707 he published a work on surgery, entitled Cours d'Opérations de Chirurgie, 8vo, which was several times reprinted; and latterly it was edited with notes by Lafayette, in two vols. This treatise was long received as a standard book on the subject. It contains many useful and pertinent observations, detailed in plain, unaffected language. Dionis is the author of two other works; the first, Dissertation sur la Mort Subite, 12mo, published in 1709, and the other Traité Général des Accouchemens in 1718, 8vo. But the last is little else than an abridgment of Mauriceau's work on the same subject. Dionis died at Paris on the 11th December 1718.