Tbe rapidity of change and the speed with which new situations are created follow the impetuous and heedless pace of man rather than the deliberate pace of nature. Radiation is no longer merely the background radiation of rocks, the bombardment of cosrnic rays, the ultraviolet of the sun that have existed before there was any life on earth; radiation is now the unnatural creation of man's tampering with the atom. The chemicals to which life is asked to make its adjustment are no longer merely the calcium and silica and copper and all the rest of the minerals washed out of the rocks and carried in rivers to the sea; they are the synthetic creations of man's inventive mind, brewed in his laboratories, and having no counterparts in nature.

To adjust to these chemicals would require time on the scale that is nature's; it would require not merely the years of a man's life but the life of generations. And even this, were it by some mirac1e possible, would be futile, for the new chemicals come from our laboratories in endless stream; almost 500 annuaHy find their way into actual use in the United States alone. The figure is staggering and its implications are not easily grasped--500 new chemicals to which the bodies of men and animals are required somehow to adapt each year, chemicals totally outside the limits ofbiologic experience.