To kill the supposed worms of the teeth, Valescus counsels three different methods, of which the first consists of the usual fumigations with seeds of hyoscyamus, onion, leek, coloquintida; the second consists in filling the carious cavity with a mixture of myrrh and aloes; and lastly, the third, in applying inside the cavity the milky juice of the tithymal, or the juice of the persicaria.[256] In regard to tartar of the teeth—which he calls _materia lapidea_, _i. e._, stony substance—Valescus says that it must be removed little by little, either with iron instruments or with dentifrices partly cleansing and partly styptic. After the tartar has been removed, it is necessary to wash the teeth often with white wine and to rub them with roasted salt.[257] Valescus, too, like the majority of ancient writers, is not at all favorable to the extraction of teeth. He says that recourse must not be had to this operation except when a tooth is the cause of most violent pain and every remedy has been of no avail. But the reasons which he gives in support of this opinion are very plausible; and whilst most of the authors who preceded him showed themselves adverse to extraction, because they considered it dangerous, he does not allude in the least to such dangers, but wishes extraction to be avoided, if possible, “because the teeth, even when they are in some parts corroded, yet nevertheless, after the pain is calmed, aid mastication and besides render the others firmer.”[258] This author agrees with Galen in considering the teeth as bones, but he is of opinion that they differ from the other bones in more than one respect; that is, first of all, on account of their sensibility; secondly, because, whilst the other bones are formed in the uterus, the teeth are formed outside the uterus; and lastly, for a reason which cannot but appear very strange to us, that is: “The bones are produced by the sperm and menstrual blood, whilst the teeth are produced by the blood in which there has remained the virtue of the sperm.”[259] This passage gives us an idea of the state of embryological knowledge of those days! PIETRO OF ARGELATA (or of La Cerlata), professor of surgery at Bologna (died in 1433), wrote a treatise on surgery in six books, in which diseases of the teeth are also taken into serious consideration. He speaks of a great number of dental instruments, which, however, are the same as those enumerated by Guy de Chauliac. His methods of cure do not offer anything very new, being for the most part identical with those of Avicenna and Abulcasis. He considers cleanliness of the teeth of the greatest importance; shows what great injury is done by dental tartar—which by him is considered a very important sign of the bad state of the teeth—he counsels the removal of it by means of scrapers, files, or the use of strong dentifrice powders; and to make the teeth white, he even advises the use of aqua fortis.