APPLICATIONS AND POSSIBILITIES 263 



The history of a thymocentric type, for instance, is predictable 

 from the very first few months of his life. Difficulties in feed- 

 ing, in habit formation and adaptation, in the reaction to infec- 

 tions, 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 chil- 

 dren, 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 equi- 

 librium among the hormones will have to be taken into account 

 in the explanation of what have hitherto been put down to lazi- 

 ness, naughtiness, stupidity, or obstinacy. 



A child's capacity for education, essentially its capacity for 

 the highest and most productive kind of life, is limited by in- 

 herent 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 environ- 

 ment 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 



