Movable prosthetic pieces are mentioned for the first time by this author. Although he is very concise in his manner of speaking of artificial teeth (this indicating that dental prosthesis was considered outside the sphere of action of the general surgeon), we nevertheless learn from him that partial sets of teeth made of ivory or hippopotamus tusks, and without special appliances for fixing them, were then in use, which, when applied in the void between the neighboring teeth, were maintained in position simply by their form. The author advises keeping prosthetic pieces very clean, removing them every evening before going to bed, and not putting them back in the mouth until they have been well cleaned. Heister also speaks of nasal prosthesis; this was then carried out by applying noses made of wood or of silver, properly painted. In cases of trismus, this author altogether rejects the forcible opening of the jaws by means of screw dilators and such like instruments, as they act too violently, and, according to him, only aggravate the morbid condition. Even the extraction of a tooth is useless in such cases, as the patient can always absorb a certain quantity of liquid food through the closed teeth. On the other hand, the author expresses himself in favor of the incision of the gums in cases of difficult dentition. According to him, convulsions and the other nervous symptoms which children are subject to during the period of dentition depend wholly on the hardness and strained condition of the gum. It is, therefore, natural that the symptoms should disappear when an incision of the gums, reaching to the tooth that is coming through, has caused the tension to cease. The author speaks very particularly of the treatment of epulis and parulis; but his views on this subject contain nothing of great importance. RENÉ JACQUES CROISSANT DE GARENGEOT (1688 to 1759), the celebrated French surgeon, speaks very little of dental surgery in his works. He declares himself averse to the carrying out of too many operations on the teeth, and especially disapproves the use of the file, because, according to him, it ruins the enamel.[400] For a long time, especially in France, Garengeot was believed to have been the inventor of the key known by his name; but he merely perfected this instrument. In fact, through a later author, Lecluse, it clearly results that the key existed before Garengeot. “For extracting,” writes Lecluse, “one may make use of the pelican that Garengeot has constructed on the English key.” In a note, he afterward adds, “that the English key is an instrument used by dentists in England.” However, it is not in the least certain that the key is really an instrument of English origin. Loder, who wrote at the end of the eighteenth century, informs us that the so-called English key was called the German key in England; it is, therefore, not improbable, that this instrument, as some maintain, had its origin in Germany.[401]