constellation differs in the number and movement of its constituent electrons from the oxygen constellation, and that both constellations are differently related to the rest of the world, but why one set of relationships should be hydrogen and the other oxygen would be revealed to him as little as it will ever be revealed to the biologist why one kind of corpuscular movement in the brain means pleasure, whereas another means pain.
Unfortunately, the biologist has no more senses than any other man; all that he tries to do is to use those he has to the best of his ability. It so happens that the senses with which he learns, and the brain with which he reflects, have evolved from simpler conditions, but however different the early stages of these organs may have been, they were elements in the fitness of his progenitors, and he believes that his natural endowments, limited though they be, are no less serviceable to himself and his fellows now than they were in pre-historic days. Today more than at any previous time in the history of civilization it is coming to be recognized that the results of the application of our senses to the study of nature are racially essential. Another and closely related truth, however, still has to fight hard for its daily bread, for it is unfortunately by no means generally known that scientific results are not, and can not be, got directly for the asking. Most men of his day, had they known about it, would have considered James Watt a fool, for instead of watching the steaming mouth of a tea-kettle, a thing which millions of men had seen before, and have seen since, and to no particular advantage either, he might have been occupied with the more obviously useful task of chopping wood for the fire; yet to these fireside dreams we can trace the whole of modern travel by steam. Perhaps Gregor Mendel, in the opinion of those who saw him pottering over his peas, would have done better to devote more time still to the affairs of his extraordinarily well-run abbey, yet upon his careful, thoughtful and beautiful observations rests the modern science of heredity, and the hope for the betterment, not only of our plants and animals, but of our very selves. Perhaps the man who hunts for frog spawn in the early spring would be better occupied removing the ashes from his cellar, yet it was a man with just this vagary whose tadpoles not only enlightened him and all the world as to the manner in which nerve fibers grow, but the methods developed in the course of these studies are now being applied for the purpose of determining the conditions under which cancerous growths occur, and consequently are freighted with the possibility of both the prevention and cure of this terrible scourge of middle and old age.
This is the method by which scientific explanations and their application come about, and however much we may regret that knowledge does not grow more simply and directly, the reason for this lies in the