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philosophies or from any of the great world religions. Nevertheless he is an optimist. He has noticed as a result of his meditations upon the arrangements within our bodies that we suffer very much from what he calls disharmonies, by which he means imperfect adaptations of structures within us to the performance of the body as a whole. He mentions various instances of such disharmonious parts. They do not seem to me quite so imposing as apparently they do to him, for many of his disharmonies are based upon the fact that we do not know that a certain structure or part has any useful rôle to play in the body. But I am inclined to suspect that in many cases it is only because we are ignorant; the list of useless structures in the human body was a few years ago very long; it has within recent years been greatly shortened, and we should learn from this experience a caution in regard to judging about these things, which, I think, Professor Metchnikoff has failed to exert duly in forming his opinions on these disharmonies. Now among the disharmonies which he recognizes is that of the great size of the large intestine, which is of such a caliber that a considerable quantity of partially digested food can be retained in it at one time. When such food is retained in the intestine, it may undergo a process of fermentation. There are many sorts of fermentation, and some of them produce chemical bodies which are injurious to the human organism. Bacteria, which will cause fermentation of this sort, do actually occur in the human intestine. Metchnikoff thinks that, as we grow old, this tendency to fermentation increases. Now the bodies produced by fermentation, the chemical bodies, I mean, get into our system and poison us. The result of the poisoning is that the native capacities of the various tissues and organs of the body are lowered, as happens in a man 'intoxicated.' All parts of a man may be poisoned, not necessarily always with alcohol, but with many other things as well, and such a poisoning Professor Metchnikoff assumes to result from intestinal fermentation. Moreover, he has further observations, which lead him to the idea that certain cells go to work upon the poisoned parts and do further damage. The cells in question are minute microscopic structures, so small that we can not at all see them with the naked eye, but which have a habit of feeding in the body upon the various parts thereof whenever they get a chance. Cells of this sort go by the scientific name of phagocytes, which is merely a Greek term for 'eating cells.' The phagocytes, for instance, devour pigment in the hair, and in old persons the production of white hair has resulted from the activity of phagocytes which have eaten the pigment which should have remained in the hair and kept its color. But the pigment of the hair is not the only thing they will attack; they will make their aggressive inroads upon any part of the body; and Professor Metchnikoff has advanced the theory that old age consists chiefly in the damage which is done