ORIBASIUS (316 to 403), the most celebrated of all the compilers who appeared during that long period of decadence, wrote, by order of the Emperor Julian the Apostate, whose physician and friend he was, a whole medical encyclopedia and later on a summary (synopsis) of this same work of his. In the books of Oribasius are found many things about dentition and diseases of the teeth, but they are all taken, substantially, from preceding authors, and therefore it is not worth while repeating them. ÆTIUS OF AMIDA, a celebrated Greek writer on medicine, lived at the end of the fifth century, and at the beginning of the sixth, and has also left us a kind of medical encyclopedia, which, being divided into four sections, each composed of four books, was called _Tetrabiblos_. He teaches that the mucous membrane of the gums, tongue, and mouth is provided with nerves from a portion of the third pair of cerebral nerves, and that the teeth, too, by a small hole existing at the end of every root, receive tiny ramifications of sensitive nerves, having the same origin. The nutrition of the teeth is understood by Ætius in the following way: The nourishment which reaches the dental nerves is not entirely assimilated by them; these only appropriate the liquid or soft part and reject the drier part. This accumulates in the alveoli, becomes by degrees more tenacious and denser, finally being transformed into osseous substance and forming the nutriment of the teeth; these, therefore, tend to grow continually, although the waste arising from the mechanical action of mastication prevents them from undergoing any real or visible growth. On the other hand, in the old, from the weakening of the nutritive functions, the teeth become thin and loose, and finally fall out.[191] Ætius advises that during dentition hard objects to chew should not be given to children, seeing that the gums being hardened by these and becoming almost callous would render the cutting of the teeth very difficult.[192] For curing parulides, he recommends emollients at the beginning of the disease, and later on astringents. But if the inflammation of the gums does not resolve and passes into suppuration, he prefers to perform the excision of the parulis, instead of making a simple incision, which might very easily cause the abscess to change into a fistula.[193] The epulis, according to Ætius, is a fleshy excrescence of the gums, brought on by inflammation. To cure it, he uses, during the inflammatory period, emollients, and then, when the inflammation has subsided, astringents and weak caustics. Lastly, if the epulis resist these remedies, he takes hold of it with a vulsella and proceeds to remove it with a small scalpel.[194] When the incision of a fistula of the gums and the use of appropriate remedies are not sufficient for curing it, Ætius advises the extraction of the diseased tooth, from which the fistula has its origin.[195]