805. But let the situation of such persons be changed; bring them, for instance, from the listlessness of retirement to the business and bustle of the city; give them a variety of imperative employments, and so place them in society as to supply to their cerebral organs that extent of exercise which gives health and vivacity of action, and in a few months the change produced will be surprising. Health, animation, and energy, will take the place of former insipidity and dulness. 806. An additional illustration, involving an important principle in the production of many distressing forms of disease will be found in the case of a man of mature age, and of active habits, who has devoted his life to the toils of business, and whose hours of leisure have been few and short. Suppose such a person to retire to the country in search of repose, and to have no moral, religious, or philosophical pursuits to occupy his attention and keep up the active exercise of his brain; this organ will lose its health, and the inevitable result will be, weariness of life, despondency, or some other variety of nervous disease. -=-=-=-=-=-=-=-=-=-=-=-= 803. What renders solitary confinement so severe a punishment to the most daring minds? What is a predisposing cause of nervous disease? 804. In what classes do mental and nervous debility prevail? 805. How can this be counteracted? 806. Give another illustration, showing how disease of the brain is induced. -=-=-=-=-=-=-=-=-=-=-=-= 807. One great evil attending the absence of some imperative employment or object of interest, to exercise the mind and brain, is the tendency which it generates to waste the mental energies on every trifling occurrence which presents itself, and to seek relief in the momentary excitement of any sensation, however unworthy. The best remedy for these evils is to create occupation to interest the mind, and give that wholesome exercise to the brain, which its constitution requires. 808. _The evils arising from excessive or ill-timed exercise of the brain, or any of its parts, are numerous._ When we use the eye too long, or in too bright a light, it becomes bloodshot. The increased action of its vessels and nerves gives rise to a sensation of fatigue and pain, requiring us to desist. If we relieve the eye, the irritation gradually subsides and the healthy state returns. But, if we continue to look intently, or resume our employment before the eye has regained its natural state by repose, the irritation at last becomes permanent, and disease, followed by weakness of vision, or even blindness, may ensue.