A third path to the fountain of youth is the conservation of health along scientific lines. This may involve medical means frequently, and it may, on occasion, even involve surgical means. It will most generally, however, involve conformity to a liberal knowledge of the ways of nature. Dr. Metchnikoff, the great Russian scientist, who spent his last years in Paris, has given to the world some illuminating discoveries upon this question of old age. He long suspected that the thing we have been calling by the name of old age, was simply the physical indication of the inroads made by disease germs to which the increasing weakness of advancing years opened a freer way. He proved to his own satisfaction, and to that of many others as well, that the apparent signs of age are the result of the ravages of a certain bacillus which inhabits the intestinal tract. He also proved the sour principle of buttermilk to be fairly fatal to that germ. One of the evidences of his latter conclusion is the fact that some of the most noted cases of longevity have been those of regular drinkers of sour milk. Physical decay seems to be only a symptom of inner attacks which will sooner or later break down an organ or result in a general collapse. It is not to be supposed that any regard for the laws of health, however strict it might be, will make it impossible ever to grow old. Physical decay is inevitable and physical death is certain. It is possible, however, to long preserve the physical condition of youth by keeping the resistance of the body at the highest possible point. This can be done only by preserving the best possible continual state of health. The sedentary character of much of the life of to-day is one of the weakening habits of our age. On the other hand, we have an army of people who are so over-exercised at their daily toil that their bodies are sapped of all vitality and their minds are robbed of all vigor. Between these two extremes lies a golden mean. Well-directed use of all the muscles and regular movement of all the organs does afford vast help in keeping the body fresh and youthful. We are the victims of another age-producing habit in the excessive quantity and richness of the food we consume. We are too willing to eat all we can get and contain. We are overdisposed, too, to truckle to the demands of palates that have been trained to enjoy unnatural and unwholesome tastes. Any experience which would drive us all back to plain living, simple eating, and active habits would probably result in large benefit to us. If our plan of living were re-established upon a childlike plane, we might again expect to enjoy childlike vitality, with its intermingling of childlike activity and childlike slumber.