More centuries have passed--we know exactly how many now from year to year. It is the nineteenth, and it is the New World; the next picture on the library wall portrayed a scene on the Western frontier of a new civilization. It is the backwoods of Kentucky, it is a pioneer settlement of three or four hundred souls, nearly a thousand miles from any hospital or dissecting-room. In the front door of his rude pioneer house stands a Kentucky country doctor, Ephraim MacDowell. His patient is before him, a woman on horseback in a side-saddle. She has just arrived, having ridden some seventy miles through the wilderness. He is assisting her to alight; and he is soon to perform, without consultation, without precedent in the ages of surgery (but not without a prayer for himself and her), by strength of his own will and nerve and by the light of the solitary candle of his own genius, an operation which made Kentucky the mother of ovarian surgery for all coming time, a new epoch of life and mercy: he going his own way to immortality as Shakespeare went his, as the greatest always go theirs--by a new path untrumpeted and alone. Another picture represented a scene in Boston in 1846, less than half a century later; for the lonely mountain peaks of progress stretching across the ages are beginning to crowd each other now; they are beginning to run together into a range of continuous discovery. That picture also shows an operating-room; and there stood the American Morton, making for the world the first merciful use of anæsthetics: with which the silence of painlessness fell upon humanity's old outcry of torture under treatment. There the doctor's pictures ended. In our own time he might have added one more for the epoch of the Roentgen Ray and another for the Finsen Light; and another for transfusion of blood; and still others crowning other mountain-tops in the new Surgery and new Medicine. Thus he had before his eyes in his library some few Ages of his Science--as it went forward and slipped back and missed the road and forgot the road, yet somehow steadily advanced across the centuries like an erring unconquerable man across his years. Not progressing however as a man grows, from infancy to decrepitude; but moving from its old age toward its youth, always toward its youth, as Swedenborg's Angels fly forever toward their Spring. It ran around his walls like a great roadway, connecting the last discoveries of his Science with the surgery of the wolf who gnaws off his imprisoned leg and with the medicine of the sick dog that eats grass. He called it his World's Path of Lessening Pain.