821. Having pointed out the evils arising both from inadequate and from excessive mental exertion, it remains to direct the attention to some of the rules which should guide us in the exercise of the brain. 822. _We should not enter upon continued mental exertion, or arouse deep feeling, immediately before or after a full meal._ Such is the connection between the mind and body, that even in a perfectly healthy person, unwelcome news, sudden anxiety, or mental excitement, occurring soon after eating, will impede digestion, and cause the stomach to loathe the masticated food. 823. The worst forms of indigestion and nervous depression are those which arise from excessive mental application, or depressed feeling, conjoined with unrestrained indulgence in the pleasures of the table. In such circumstances, the stomach and brain react upon and disturb each other, till all the horrors of nervous disease make their unwelcome appearance, and render life miserable. Too many literary men and students know this from sad experience. 824. _We should engage in intense study in the early part of the day._ Nature has allotted the darkness of the night for repose, and for restoration by sleep of the exhausted energies of mind and body. In the early part of the evening, if study or composition be ardently engaged in, the increased action of the brain, which always accompanies activity of mind, requires a long time to subside. If the individual possesses a nervous temperament, he will be sleepless for hours after he has retired, or perhaps be tormented by unpleasant dreams. -=-=-=-=-=-=-=-=-=-=-=-= 822. Why should we not arouse deep feeling immediately before or after eating a full meal? 823. How are the worst forms of indigestion and nervous depression produced? What class of men know this from sad experience? 824. What evils arise from studious application at night? -=-=-=-=-=-=-=-=-=-=-=-= 825. It is, therefore, of great advantage to enter upon intense mental application early in the day, and to devote several of the hours which precede bedtime to entertaining conversation, music, and lighter reading. The vascular excitement previously induced in the brain by study, has then time to subside, and sound, refreshing sleep is much more certainly obtained. This rule is of great consequence to those who are obliged to undergo much mental labor. _Observation._ The idea of gathering wisdom by burning the "midnight oil," is more poetical than profitable. The best time to use the brain is during the day.