PIERRE DIONIS, a celebrated surgeon and anatomist of Paris (died 1718), in his _Anatomie de l’homme_,[390] admits the possibility of a double dental series, holding the case, however, to be of very rare occurrence. Another work of his, entitled _Cours d’operations de Chirurgie_, wherein he treats very extensively of diseases of the teeth and mouth, and their surgical cure, is of much more importance in relation to dentistry. He recognizes the high importance of this part of surgery, but expresses the opinion that one of the dental operations, that is the extraction of teeth, ought to be left entirely to the tooth-pullers, not only because they are, by reason of great practice, better qualified to perform it than general surgeons, but also because the output of force required for this tooth-pulling operation renders the hand heavy and tremulous, and, lastly, because, according to him, it always has something of charlatanism about it. (This is a luminous example of how preconceived ideas can influence the minds even of men of the greatest talent.) Pierre Dionis, like many of the preceding authors, had frequently occasion to observe cases of epulis. He speaks at great length of the treatment of this affection, as well as of parulis, but says nothing on the subject of sufficient importance to be worth recording. Dental operations, according to Dionis, are of seven kinds: 1. _The opening of the dental arches in the case of spasmodic constriction of the jaws._ This operation, of the greatest importance for nourishing and keeping patients alive, is carried out by means of a lever and of a screw dilator. 2. _The cleaning of the teeth._ For this, as for the other operations, says Dionis, a certain amount of skill is required. The author advises the use of gold instruments if one be called upon to clean the teeth of persons of rank. This appears rather strange in the present levelling times, but Pierre Dionis lived in the days of Louis XIV, whose doctor he was, that is, in a period of unbridled luxury, when the nobles and those in power would have nothing in common with the lower classes. 3. _Operations for the preservation of the teeth._ These, says Dionis, are of the greatest importance, it being necessary to oppose a barrier to the destructive processes of the teeth. Caries, when so situated as to permit of it, ought to be scraped away; for approximal caries one ought to have recourse to the file; in the case of caries of the triturating surfaces, cauterization should be used, by applying a drop of oil of vitriol with a miniature paint brush. Should the caries, however, be in a very advanced stage, it is better to make use of the cauterizing iron. But in cases of intense and persistent pain there is no other remedy than extraction.