A child's capacity for education, essentially its capacity for the highest and most productive kind of life, is limited by inherent factors. These factors are two: the quality of the nerve tissue, its ability to make a number of associations, and the quantity of the internal secretions, measured by the maximum obtainable in a given situation. These inherent factors explain, too, why children born and bred in virtually the same environment show the most extreme differences in educability. That the differences are inherited was made evident by Galton's finding that the chance of the son of an eminent man exhibiting eminent ability was 500 times as great as that of the son of a man taken at random. Every baby, then, is born with a combination of nerve cells and ductless glands which determine its capacity for mental development, that might never be realized, but could never be exceeded. If, in any family, minor differences in educability are observed, they can be put down to disturbance of these two factors occurring after the fertilized germ cell had started to divide and reproduce itself. But any marked falling off in either the nervous or endocrine factors has to be considered pathologic, due to an impairment of them by adverse environment. Recent studies have amply established that the proportion of certifiable mental defectives, and of a much larger class, the subnormal but not certifiable class, is progressing by leaps and bounds. It is perhaps the most absurd frailty of our present system of education that it takes almost no account of innate differences in educability. To spend money upon the teaching of these children along lines where they are unteachable is not only waste pure and simple, but crime, for it deprives the educables of their just due. These, of course, are the crude and simple lines upon which the finer and more complex evolution of the endocrine problems of the school child will build. The fine art of education itself is crude and gross and simple compared with what it might be, even as a beginning. The science of education has yet to begin, as the offspring of that science of the future, to which knowledge of the internal secretions will contribute no little, the science of puericulture. VOCATIONAL EDUCATION