effect of any scientific discovery can only be measured when we are in a position to judge of the conditions in which it may be applied, and the further discoveries which may affect it--a consideration which will help us against the danger of undue caution in estimating the possible developments of recent discovery when utilised in the conditions of the next century and reinforced by inventions and discoveries yet to come. A like caution will, however, teach us to restrain our expectations from the new knowledge which radium appears to be gradually unfolding, not because there is any doubt that radio-activity will ultimately bring priceless gifts to civilisation, but because in our present ignorance of all but a few facts concerning it we can form no possible conjecture as to the lines these gifts will follow. Already we seem to have seen in some of the radium experiments one "element" turn into another. If this should develop until we acquire the power which used to be dreamed of as transmutation, the social and economic upheavals which would result beggar imagination. [16] The photographic effect of Röntgen rays has already [17] been the subject of a suggestion, and even the facts now remotest from practical use in connection with the rays of various sorts so much discussed in the scientific newspapers will no doubt be utilised in a manner or in manners far removed from the limited employment in therapeutics already found for them. And indeed medicine, not the most progressive of modern sciences, will no doubt make vast strides during the period under discussion. It would be altogether fallacious to forecast the position and probable achievements of medical science in a century's time on the line of simple development from the practice of to-day. The changes will be revolutionary rather than evolutionary. When it is remembered that only fifty years ago limbs were hacked from the quivering flesh of the sentient patient, held down by muscular assistants lest the violent struggles of his agony should embarrass the surgeon, and that wounds of all sorts festered and decayed until a hospital reeked with their impurity--in other words, that discoveries so great as anæsthesia and antisepsis are well within living memory--we need not hesitate to predict for the present century changes in medical and surgical science almost inconceivable by the light of our present attainment. Anæsthetics--of which the local kinds, as cocaine and eucaine, are of entirely recent use--represent an advance in one direction. Antiseptic surgery, which is the prevention and correction of blood and wound-poisoning by chemical disinfectants, represented an advance of a different kind. But antisepsis is already on the point of being superseded by the far more rational and scientific method of asepsis, or the exclusion from open wounds of all the germs which can set up inflammation and festering. The change is typical.