Brinkley's operation, for it is no less than a discovery, would have meant to the world in the prolongation of the lives of those benefactors in all fields of human endeavor, Literature, Science, Art, etc., if it had been known and understood when Shakespeare wrote, when Darwin worked, when Rubens painted, and when Patti sang. It will please your fancy to picture what might have been, but we have before us the consideration of what is, and it is more than comforting to know that we shall deal here with the hard cold facts of what is being done today, and will be done tomorrow. This is no poet's dream, but the stern reality of a young surgeon's work in hospital, extending over three memorable years of achievement in a virgin field. Dr. Brinkley has worked out his problem alone, save for the devoted aid of his wife, who is also a licensed physician. He is today a poor man, and expects to remain so, because he has refused every alluring offer made him looking to the establishment of this Goat-Gland operation as a commercial proposition on a big scale. He is governed by his ethical vows, and retains his independence, but the world would call him a fool for not turning his discovery to his greatest pecuniary profit. Since he prefers to remain true to his ideals in this matter it is for us at least to be thankful, and accord him the recognition to which the scientist is entitled who puts his work above his profits. Chicago, April, 1921. CHAPTER I DR. BRINKLEY'S THEORY We are not privileged to be discursive in a little book which seeks to hit the nail on the head in every paragraph, drive it home in every page, and clinch it in every chapter, and there would be no excuse, therefore, for sketching, even in brief outline, the history of the various attempts that have been made, from Brown-Sequard, with his Elixir, to Metchnikoff, with his benevolent bacteria of the intestinal tract, to extract from Life its secret of human longevity. It has been a long quest, and, in the main, fruitless, though it might be said in fairness that Brown-Sequard's method of using the expressed testicular juice as a medicine, by mouth or injection, for the renewal of youth, was probably the true parent of the present familiar method of using the extracts of various glands, or the pulverized substance of the glands themselves, notably the thyroid and the adrenal, as medicines to be taken internally for the relief of various diseased conditions. The constant objection to such form of medication is, of course, that when the medicine is stopped the good results stop, so that a temporary relief is the utmost that can be hoped for from the method. Genius is synthetic, elliptic, sudden, but always clear and sure. Dr. Brinkley began with a theory, and by no means a new theory. From the theory he deduced rapidly, and acted. The results of the acts proved the truth of the theory. That theory has been variously stated, its most familiar