In Pope Julius' Museum in Rome there is a specimen of a gold cap made of two plates of gold riveted together and also riveted to bands of metal which were fastened around the neighboring teeth in order to hold the cap in place. This is from later Republican times at Rome. At the end of the Republic and the beginning of the Empire there appear to have been many forms of dental appliances. Martial says that the reason why one lady's teeth--whose name he does not conceal--are white and another's--name also given--were dark, was that the first one bought hers and the second still had her own. In another satiric poem he describes an elderly woman as so much frightened that when she ran away her teeth fell out, while her friends lost their false hair. Fillings of many kinds were used, dentrifices of nearly every kind were invented, and dentistry evidently reached a high stage of development, though we have nowhere a special name for dentist, and the work seems to have been done by physicians, who took this as a specialty. While in the Middle Ages there was, owing to conditions, a loss of much of this knowledge of antiquity with regard to dentistry, or an obscuration of it, it never disappeared completely, and whenever men have written seriously about medicine, above all about surgery in relation to the face and the mouth, the teeth have come in for their share of scientific and practical consideration. Aetius, the first important Christian writer on medicine and surgery, discusses, as we have seen in the sketch of him, the nutrition of the teeth, their nerves, "which came from the third pair and entered the teeth by a small hole existing at the end of the root," and other interesting details of anatomy and physiology. He knows much about the hygiene of the teeth, discusses extraction and the cure of fistula and other details. Paul of AEgina in the next century has much more, and while they both quote mainly from older authors there seems no doubt that they themselves had made not a few observations and had practical experience. It was from these men that the Arabian physicians and surgeons obtained their traditions of medicine, and so it is not surprising to find that they discuss dental diseases and their treatment rationally and in considerable detail. Abulcasis particularly has much that is of significance and interest. We have pictures of two score of dental instruments that were used by them. The Arabs not only treated and filled carious teeth and even replaced those that were lost, but they also corrected deformities of the mouth and of the dental arches. Orthodontia is sometimes said to be of much later origin and to begin many centuries after Abulcasis' time, yet no one who knows of his work can speak of Orthodontia as an invention after him. In this, however, as in most of the departments of medicine and surgery, the Arabs were merely imitators, though probably they expanded somewhat the practical knowledge that had come to them.