Observations. 1st. Moderation in mental exertion is more necessary in old age than in early or mature years. In youth and manhood, the exhaustion of the brain from over-excitement may be repaired, but no such result follows over-exertion in the decline of life. “What is lost then, is lost forever.” At that period, the brain becomes excited, and is soon exhausted when forced to protracted and vigorous thought. Sir Walter Scott and President Harrison afford sad examples of premature death from overtasked brains at an advanced period of their lives.
2d. If the mind is incessantly engaged in the contemplation of the same object, there is danger from over-exertion of the brain at any period of life, but more particularly in old age. The more limited the sphere of mental action, the greater the danger of the brain being over-exercised. Hence the frequency of nervous diseases in poets, mathematicians, and musicians.
820. What often manifests itself from the want of proper intervals of rest? Why is moderation in mental action necessary in old age? What is the effect if the mind is incessantly engaged in the contemplation of the same object?
CHAPTER XL.
HYGIENE OF THE NERVOUS SYSTEM, CONTINUED.
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.