Fourthly. We found a certain degree of warmth was favorable; that is, of course, always present in the living body, and in choosing a good non-conductor of heat as your plugging material, it is with reference to the secondary effects of caries, the pain caused by thermal extremes, and not with special reference to the disease itself. Indeed, could we obtain a substance which would combine the resistance to organic and chemical action that gold does with the poorness of conducting power of gutta percha, it would be a great advance. The presence of air in the decayed tooth is also prevented by the mechanical means; while lastly you substitute an artificial tissue to resist in place of the dentine and enamel that is gone. Indeed it seems to be that the whole process of successfully filling a decayed tooth is one of the most perfect examples of antiseptic treatment I am acquainted with. I doubt not there will be further advances made in your technique, but the principles will not change. I believe it quite likely that it will prove desirable to more thoroughly disinfect the carious cavity before filling than is always done now, and it may prove possible to devise some material which, either by its hardness or by its chemical constitution, or by some antiseptic incorporated with it, will longer resist the destruction due to attrition and to chemical and micro-organic action than the ones now in use. To recur to the main problem of our paper—the relief of pain—is it not true in this class of cases that after the first effects are stilled, its recurrence is prevented by affording artificially that immunity to the pulp from peripheral irritation which it possesses in health? Disease of the peridental membrane causes a characteristic pain, but one which need not long detain us. From the fact that it is nearly always secondary and not primary, its treatment should first of all necessitate the removal of the originating cause. The spread of inflammation or decomposition from the pulp to the periosteum which so often occurs can be better accounted for by the hypothesis of the action of micro-organisms than by any other supposition. Moreover, in the advanced cases, where pus has formed, the same cardinal indication of treatment, viz., proper drainage, obtains here as in other departments of bone surgery. We have already spoken of the constitutional poisons, syphilis and mercury and phosphorus, which may be causes of this form of trouble, and I would only like to say one more word, and that is in the way of treatment.