Occasionally it has seemed to me that you can stop the further progress of a periostitis, if you get it in an early stage, and prevent it from going on to suppuration. I remember one case of a gentleman who applied to me for a very painful gumboil in his lower jaw opposite the first molar. The gum was swollen and reddened, and a well-marked phlegmon could be felt. I gave him fairly large doses of mercury for a couple of days, and it gradually melted away. There was no suspicion of syphilis in this case. Another remedy I believe to be of great value in treating neuralgia of the face starting in periosteal irritation, is phosphorus. The best form in which to administer this remedy is the preparation known as Thompson’s solution. I can testify to this from personal experience. Some twelve years ago I suffered from periostitis of the first bicuspid of the upper jaw on the right side. A couple of years later, while working hard, I had an attack of intense neuralgia of the entire second division of the fifth. When it subsided, it left some periosteal thickening at the exit of the nerve from the infra-orbital foramen; and ever since then, whenever I get run down by overwork or worry, the same pain crops out. But I have found that a few doses of phosphorus will completely hold it in check; and in one or two patients, since then, I have seen the same fact, that in the neuralgia due to periosteal irritation this remedy holds a high place. It has seemed to me highly significant that the two drugs, mercury and phosphorous, which in continued toxic doses cause this very class of diseases, should in physiological doses be curative. But this is in entire consonance with the general laws of tissue irritation, and the therapeutic fact that certain drugs acting through the nervous system stimulate in small doses and narcotize in large ones. The last type of dental pain I will speak of is that arising from pressure due to hypertrophy of the cement. Where this is not due to the peripheral irritation of a carious tooth, the causation is both interesting and obscure. It has seemed to me that we must postulate the agency of a constitutionally acting cause to account for certain of these cases. I think it quite probable that in certain cases a well-marked gouty diathesis will be found underlying this form of disease; and a similar constitutional error must be invoked to explain the allied cases of calcification of the pulp.