Page:Popular Science Monthly Volume 80.djvu/297

Rh for girls safely be modeled after that for boys? What time in the day should exercise in physical training be given? How should it alternate with other school studies? Can it ever safely replace the old-fashioned free "recess"? Just what does it mean, physiologically, for a muscle to be "trained"? Which of the half dozen or more theories is the correct one? How far can training be bunched? Does training produce fatigue bodies and anti-bodies, as Weichardt thinks he has demonstrated?

How many hours daily should children study? Can any one disprove Dr. Weir Mitchell's assertion (which seems to be the belief of most psycho-pathologists) that children could accomplish as much as they do now if the school day were only half as long? What is the most favorable alternation of work and rest periods in mental hygiene? What is the diurnal course of mental (also moral) efficiency? When is the assignment of home study justifiable? How do the results of home study compare in quality and quantity with school study? Is there much or little ground for the frequent charges of overpressure made against the schools? Is school overpressure responsible for any of the recent and marked increase in child suicides?

Investigations into the sleep of school children show that they sleep on the average nearly 25 per cent, less than "authorities" have usually set as a safe norm. Is there a real sleep insufficiency of 25 per cent., or has the amount needed been overestimated? In the matter of sleep what are the safe limits of habit adaptation? What is the relation of sleep to school progress, nutrition, morbidity and conduct?

The human eye was evolved to satisfy the demands of ordinary vision—that is, to make on the average 15 or 20 movements per minute, under conditions which permit frequent shifts of accommodation and convergence. The work of the school demands of the immature eye that it execute for several hours a day an average of 150 to 200 separate movements per minute with as many rifle-aim fixations and with a uniformly intense strain of the muscles of accommodation and convergence. What is the relative importance of these factors as compared with heredity in the etiology of ocular defects? How does malnutrition affect the eye? How much truth is there in Dr. George M. Gould's assertions regarding the reflex effects of eye-strain upon general health? What is the minimum size of type that should be permitted for children of different ages? What are the optimum norms for width of stroke, spacing of letters and words, length of lines, color of paper, and intensity of light? Is the complete conservation of vision possible?

What conditions of health obtain among the one-half million school teachers in the United States? What kind of physical constitution