To hit off the happy medium between over- and under-work is no easy task even to those who have the necessary knowledge, on the one hand, and the liberty to arrange their own scheme of occupation, on the other. But, for one person who is injured by doing too much, I quite believe with Dr. Wilkes that many may be found who are sustaining serious damage from not having enough mental stimulus. The listless vacuity in which so many of the well-to-do classes spend their lives, the want of any incentive to exertion, and the absence of any attempt at real thought which the wide-spread prevalence of ready-made opinions in our periodical literature directly encourages, must cause more or less degeneration of intellectual power. Under these conditions the brain gradually loses its healthy tone, and, although quite equal to the daily calls of a routine and uneventful existence, it is unable to withstand the strain of special sudden emergency, and, when a heavy load of work is unexpectedly thrown upon it in its unprepared state, then we see all the worst consequences of what may be called overwork develop themselves.