As to the use of the file, far from rejecting it entirely, as does Martin, he holds it necessary in many cases for planing down points and sharp edges of broken teeth, as well as for removing, at least in a measure, the inconvenience and deformed appearance caused by irregular teeth. He says the file may be used without causing the slightest harm, if one takes care not to approach the inner cavity of the tooth too nearly, and above all not to penetrate right to it, which would give rise to intolerable pain. Such an accident, he adds, may happen much more easily when, instead of using the file, whole pieces of teeth are removed with the excising forceps. This author acquaints us with a tooth powder, much used in his time, especially by Parisian ladies. The ingredients were powdered cuttle fish, coral powder, cream of tartar, Armenian bole, and powder of red roses. At that time artificial teeth were generally made of ivory; Nuck, however, observes that it soon becomes yellow by the action of food and drink, and of the saliva itself. He therefore recommends, instead, the use of hippopotamus’ tusks, giving the preference to the whitest. According to Nuck, artificial teeth made of hippopotamus’ tusks would be capable of preserving their color even for seventy years. In the case of all the teeth of the lower jaw being wanting, the entire dental arch ought to be framed in with a single piece of ivory or tusk of hippopotamus.[382] CARLO MUSITANO, a celebrated Neapolitan doctor (1635 to 1714). According to Carlo Musitano, the real cause of toothache consists in the irritant action of saline or acid particles on the extremely thin membrane that lines the alveoli or on the exquisitely sensitive nerves of the teeth. As he believes, these particles have an angular form, sometimes pointed or even hooked, and they reach the sensitive parts either directly from the outside, through the air, the food or drink (especially when the teeth are already decayed), or else through the blood and other humors, which often, by reason of their deteriorated quality, contain great quantities of such irritant particles. Among the various influences which may be conducive to toothache, atmospheric conditions ought also to be included; thus, says the author, the inhabitants of the Baltic littorals, and other northern peoples, are very subject to toothache, for the reason that in those regions the air contains, in abundance, saline particles of various kinds which penetrate into the organism by the act of respiration. It is said, on the contrary, that in Egypt, where the air is remarkably mild, the teeth are not subject either to pain or to decay. Musitano, too, believes in worms in the teeth, but does not admit, as preceding authors had done, that they generate spontaneously. He holds instead that they result from the eggs of flies and other insects, which, together with food, are introduced into the carious cavities and there develop by the heat of the mouth.