In 1759 Jourdain described in the _Journal de Médecine_[488] an improved pelican and another instrument to be used for straightening teeth inclined inward. Two years later he published his treatise on the diseases of Highmore’s antrum and on fractures and caries of the maxillary bone.[489] After this, appeared his book on the formation of the teeth.[490] He therein describes with great accuracy the dental follicle from its first appearing to the moment of birth, following it throughout its evolution. This lengthy book is most interesting, for it is not a mere compilation, but gives the results of personal research and experience. But by far the most important of all the works of this author is his treatise on the diseases and surgical operations of the mouth.[491] This book went through several French editions, was translated into German in 1784, and has had, besides, two English editions in America of comparatively recent date, that is, at Baltimore in 1849, and at Philadelphia in 1851; all of which proves the great value of the work; it treats, however, much more of general surgery of the mouth and neighboring regions than of dental art properly so called. The first volume of 626 pages is almost entirely dedicated to the diseases of the maxillary sinus, which, for this author, were ever the object of favorite and particular study. He is not in favor of carrying out irrigation of the antrum through the mouth, even when an alveolar opening has resulted spontaneously through the extraction of a decayed tooth; he prefers instead, whenever this is possible, the reopening of the nasal orifice, by means of sounds and cannulæ adapted for the purpose, that is, varying in thickness and in length, and curved according to the necessities of the case. The natural opening of the antrum being reëstablished, one irrigates the cavity through it by means of a cannula to which a small syringe has been screwed. When the teeth are sound, notwithstanding the diseased condition of the antrum, Jourdain is absolutely contrary to the performing of the Cowper-Drake operation. When, on the contrary, the malady owes its origin to decayed teeth, Jourdain extracts them, but, as already said, carries out the detersive and medicated injections through the natural opening. The author divides the collections of the maxillary sinus into purulent and lymphatic. The purulent are painful and corrode the bone, the lymphatic are not painful and do not corrode the bone, but distend and soften it, producing external tumefaction which yields to pressure, and, on this being diminished, gave out a characteristic sound. These so-called lymphatic gatherings referred to by Jourdain are none other than mucous cysts of the maxillary sinus. Also the other diseases of Highmore’s antrum (polypi, etc.) are taken by this author into attentive and minute consideration.