It has always seemed to me that the story of Medieval Dentistry presented an even better illustration of a great anticipatory development of surgery. This department represents only a small surgical specialty, but one which even at that period was given over to specialists, who were called dentatores. Guy de Chauliac's review of the dentistry of his time and the state of the specialty, as pictured by John of Arcoli, is likely to be particularly interesting, because if there is any department of medical practice that we are sure is comparatively recent in origin, it is dentistry. Here, however, we find that practically all our dental manipulations, the filling of teeth, artificial dentures, even orthodontia, were anticipated by the dentists of the Middle Ages. We have only the compressed account of it which is to be found in text-books of general surgery, and while in this they give mainly a heritage from the past, yet even this suffices to give us a picture very surprising in its detailed anticipation of much that we have been inclined to think of as quite modern in invention and discovery. Medicine developed much more slowly than surgery, or, rather, lagged behind it, as it seems nearly always prone to do. Surgical problems are simple, and their solution belongs to a great extent to a handicraft. That is, after all, what chirurgy, the old form of our word surgery, means. Medical problems are more complex and involve both art and science, so that solutions of them are often merely temporary and lack finality. During the Middle Ages, however, and especially towards the end of them, the most important branches of medicine, diagnosis and therapeutics, took definite shape on the foundations that lie at the basis of our modern medical science. We hear of percussion for abdominal conditions, and of the most careful study of the pulse and the respiration. There are charts for the varying color of the urine, and of the tints of the skin. With Nicholas of Cusa there came the definite suggestion of the need of exact methods of diagnosis. A mathematician himself, he wished to introduce mathematical methods into medical diagnosis, and suggested that the pulse should be counted in connection with the water clock, the water that passed being weighed, in order to get very definite comparative values for the pulse rate under varying conditions, and also that the specific gravity of fluids from the body should be ascertained in order to get another definite datum in the knowledge of disease. It was long before these suggestions were to bear much fruit, but it is interesting to find them so clearly expressed.