A number of attempts have been abortive in this field. Why they have failed to arouse the ardor of the parent has puzzled some of the pioneers. Child-culture as the foundation of all systems of education has continued more or less of a hope rather than an achievement because of a lack of appreciation of the different constitutional varieties of children. A certain amount of attention has been lavished upon children needing special attention, those mainly suffering from insufficient development of one sort or another. In the last decade or so, an endeavour to focus upon the exceptional child, exceptional in intelligence or some special creative endowment, has started an interesting movement. All of them have suffered from the fallacies and troubles of the pure psychologist who would handle mind as an entity in a vacuum. A realization of the different physical and psychic educational needs of various children will arrive only when we see them as built differently. Just as shoddy and silk, cotton and wool, alone or in combination, all possess different qualities as wearing material, so different children have varying capacities for the wear and tear of education. The endocrine classification of the human race, applied to children, will here yield a harvest to the educator and to the country. Nothing is more evident than the diversified nature of the needs of the various internal secretion types, once they are realized as such. The history of a thymocentric type, for instance, is predictable from the very first few months of his life. Difficulties in feeding, in habit formation and adaptation, in the reaction to infections, in social play and so on, one may expect for him. The course of events for the other endocrine types also follow laws of their own. It will be above all in the _understanding_ of children, their make-up, reactions and powers, that the biologist will achieve some of his finest triumphs. The educator will have to take account of the state of the pituitary in estimating the normal intelligence, or influencing the abnormal or subnormal intelligence. As well will he have to consider the thyroid in the child whose conduct is refractory, even though his proficiency in his studies is excellent. And the condition of the adrenal will be ascertained in the types that tire easily, and that seem unable to make the effort necessary or desirable. Periodic seasonal and critical fluctuations in the equilibrium among the hormones will have to be taken into account in the explanation of what have hitherto been put down to laziness, naughtiness, stupidity, or obstinacy.