In regard to the first operation, the author first of all examines the various causes of the constriction of the dental arches, and according to the various nature of this, he indicates in what cases it is fitting to have recourse to the forced opening of the jaws by means of appropriate dilators, and in what cases it is best to avoid it. In the latter case one must seek to feed the patient in other ways—that is, either by alimentary clysters, or by a little tube passed through a space already existing or purposely made by the extraction of one or two teeth; or else by letting a cannula reach down to the pharynx, through the nose, or, lastly, by introducing a cannula into the oral cavity through the free space existing behind the last molars. But in regard to this last method, Fabricius notes that if the constriction is of a spasmodic nature, the spasm may affect not only the elevator muscles of the jaws, but also those that govern deglutition, including sometimes even those of the tongue itself, and in this case, as the food introduced into the oral cavity could not be swallowed, it is preferable to convey it directly into the pharynx, by means of a cannula passed through the nostrils. The second of the above-mentioned operations[322] is designed, says Fabricius, to take away the dirtiness of the teeth and the bad odor of the mouth (_dentium immunditiam et oris fœtorem tollit_). The dental tartar (_ostracoderma_) must be removed by slender instruments of an appropriate shape, which, for people of high position (_promagnatibus_) shall be made of silver. This advice is sufficient to make us understand that Fabricius, although an excellent surgeon, had no practice in dental operations; otherwise he would have known that the hardness and adhesion of tartar is generally so great that its removal absolutely requires scrapers of tempered steel and not of a soft metal like silver. To arrest caries, he first drops into the carious hollow, by means of a small silver funnel, some drops of oil of vitriol, or of some other caustic liquid; and then he performs actual cauterization with appropriate instruments; after which the cavity is filled with gold leaf (auro foliato). When one or more teeth have appeared in an irregular position and offend the walls of the oral cavity or else the tongue, the excision (resection) of the tooth or teeth must be performed with a pair of strong pincers, whose shape must vary according to whether the teeth are situated externally or internally with regard to the dental arches. But as after the resection there will almost always remain some points or sharp irregularities, which by their presence would continue to irritate the soft parts, it will be necessary to remove these irritating prominences by means of the file.