“Sir Walter Scott, according to Carlyle, was the only perfectly healthy literary man who ever lived.  He gave it as his deliberate opinion, in conversation with Basil Hall, that five and a half hours form the limit of healthful mental labor for a mature person.  ’This I reckon very good work for a man,’ he said.  ‘I can very seldom work six hours a day.’  Supposing his estimate to be correct, and five and a half hours the reasonable limit for the day’s work of a mature intellect, it is evident that even this must be altogether too much for an immature one.  ’To suppose the youthful brain,’ says the recent admirable report, by Dr. Ray, of the Providence Insane Hospital, ’to be capable of an amount of work which is considered an ample allowance to an adult brain is simply absurd.’  ’It would be wrong, therefore, to deduct less than a half-hour from Scott’s estimate, for even the oldest pupils in our highest schools, leaving five hours as the limit of real mental effort for them, and reducing this for all younger pupils very much further.’

“But Scott is not the only authority in the case; let us ask the physiologists.  So said Horace Mann before us, in the days when the Massachusetts school system was in process of formation.  He asked the physicians in 1840, and in his report printed the answers of three of the most eminent.  The late Dr. Woodward, of Worcester, promptly said that children under eight should never be confined more than one hour at a time, nor more than four hours a day.

“Dr. James Jackson, of Boston, allowed the children four hours schooling in winter and five in summer, but only one hour at a time; and heartily expressed his detestation of giving young children lessons to learn at home.

“Dr. S.G.  Howe, reasoning elaborately on the whole subject, said that children under eight years of age should never be confined more than half an hour at a time; by following which rule, with long recesses, they can study four hours daily.  Children between eight and fourteen should not be confined more than three-quarters of an hour at a time, having the last quarter of each hour for exercise on the play-ground.

“Indeed, the one thing about which doctors do not disagree is the destructive effect of premature or excessive mental labor.  I can quote you medical authority for and against every maxim of dietetics beyond the very simplest; but I defy you to find one man who ever begged, borrowed, or stole the title of M.D., and yet abused those two honorary letters by asserting under their cover that a child could safely study as much as a man, or that a man could safely study more than six hours a day.”