In the normal, well-organized adult brain the various areas are closely knit together by association pathways or fibers,[50] which renders it possible to employ in particular direction the energies generated over large regions. But this development comes relatively late and is not fully completed under about thirty-three years of age, it is now believed. It is in a measure, then, impossible for the young child to utilize the energies produced in one part of the brain in activities involving remote sections. One who observes little children in their spontaneous activities can not fail to note evidences in plenty in illustration of this principle. It should be apparent, then, why a school programme so arranged that a lesson in writing is followed by one in written language, this by written number, and this in turn by written spelling, or possibly by a written reproduction of a lesson in Nature or literature, is admirably suited to exhaust the overused areas of pupils' brains, whereupon the mental and physical effects of fatigue make their appearance. In one of the large cities of our country the amount of time spent in writing was calculated for all the grades in the schools, and it was found that at least one hour was required of the children in every grade, and in the fourth and fifth grades they were engaged for two hundred minutes every day in writing in some form or other. [Footnote 50: Donaldson, The Growth of the Brain, chapters ix to xiii.] Doubtless every one has observed how readily he becomes fatigued when he is engaged in activities demanding very delicate muscular adjustments--threading a needle, for instance. Work of this character involves particularly the higher co-ordinating areas of the brain, those controlling the more precise and elaborate adjustments of the body, and this work makes large demands upon one's nervous energy. This seems to be pre-eminently true of the child, in whose brain the highest regions are yet comparatively undeveloped, so that much exercise of them leads quickly to exhaustion. Those activities, then, which compel a great amount of exact co-ordination of young children will easily fatigue them. The writer has for some time been observing the effect of various sorts of playthings upon the activities, particularly upon the emotions, of two young children. He has noticed that those plays requiring most accurate co-ordination, as stringing kindergarten beads with small openings or writing with a hard lead pencil, will quickly produce fatigue, shown in irritability, discontent, and lack of control; while those plays which employ the larger muscles, as working in sand or drawing a cart, are more enduring in their interest and are not attended by such disagreeable after effects. It is customary, however, in many homes and schools to require of the youngest children the finest work in the management of the smallest tools and materials, such, for instance, as writing on