Page:Popular Science Monthly Volume 71.djvu/478

472 of the most impressive sights which I have ever seen has been the sight of the heart of a quadruped, a dog, continuing to beat after it had been taken out from the body. The dog was dead—the rest of his body was dead—but the heart lay upon the physiologist's table beating. The experimenter could supply it with the necessary circulation. He could give stimuli to it, and under these favorable conditions make important discoveries in regard to the functioning of the heart. So too I myself made experiments upon a muscle once part of a living dog, separated entirely from the parent body, supplied with its own artificial circulation, and from those experiments was able to discover some new unexpected results in regard to the nutrition of the muscle, and the changes which chemically go on in it. This over-living, then, of the parts of the body, their separate life, is something which we must familiarize ourselves with, and the great importance of which we must carefully acknowledge, for much of the benefit which the medical practitioner is able to render to us and to our friends to-day is due to the knowledge which has been derived experimentally from the study of the over-living or surviving parts of a body which as a whole was dead.

Death is not a universal accompaniment of life. In the lower organisms death does not occur as a natural and necessary result of life. Death with them is purely the result of an accident, some external cause. Natural death is a thing which has been acquired in the process of evolution. Why should it have been acquired? You will, I think, readily answer this question if you hold that the views which I have been bringing before you have been well defended, by saying that it is due to differentiation, that when the cells acquire the additional faculty of passing beyond the simple stage to the more complicated organization, they lose something of their vitality, something of their power of growth, something of their possibilities of perpetuation; and as the organization in the process of evolution becomes higher and higher, this necessity for change becomes more and more imperative. But it involves the end. Differentiation leads up, as its inevitable conclusion, to death. Death is the price we are obliged to pay for our organization, for the differentiation which exists in us. Is it too high a price? To that organization we are indebted for the great array of faculties with which we are endowed. To it we are indebted for the means of appreciating the sort of world, the kind of universe, in which we are placed. To it we are indebted for all the conveniences of existence, by which we are able to carry on our physiological processes in a far better and more comfortable manner than can the lower forms of life. To it we are indebted for the possibility of those human relations which are among the most precious parts of our experience. And we are indebted to it also for the possibility of the higher spiritual emotions. All this is what we have bought at the