835. The continuance of healthy and vigorous action in the matured physical, mental, and moral powers, requires frequent and regular action, alternated with rest, as much as in their development. Consequently, those who cultivate one or two of these faculties, to the neglect of the others, exhibit a marked deficiency of acuteness and vigor in those not exercised. This defect reacts on the powers that are vigorous, diminishing the energy and deteriorating all the other faculties of man. _Observations._ 1st. If the principles before mentioned are true, the adult, as well as the child, should spend a part of each day in some proper physical employment; another portion should be appropriated to intellectual pursuits; while another should be sedulously devoted to the cultivation of the moral feelings. 2d. Disease of the corporeal system more frequently occurs when only one set of faculties is used than when all are equally employed. This is particularly true of nervous and mental disease, which follows and is caused by either high intellectual action, or intense moral emotions, without a due amount of physical exercise. -=-=-=-=-=-=-=-=-=-=-=-= How is the "dreaming out" of problems explained? 834. What is said of the culture of the intellect? What schools are preferable in the education of youth? Why? 835. What is the effect of cultivating only one faculty of the mind? Give observation 1st. Observation 2d. -=-=-=-=-=-=-=-=-=-=-=-= 836. _The brain can exercise its full force upon only one object at a time._ If its energies are directed to two or more operations, neither will receive that full power of exertion that it would if only one object had engaged the mind. Although the brain will direct several operations at the same time when only slight mental effort is required, yet when one operation becomes difficult, or demands special attention of the mind, the other will be suspended. This is illustrated in social conversation while walking. Let it become necessary to concentrate the nervous power upon the motor organs, and the conversation declines or ceases. 837. In acquiring an education, or in pursuing any profession or trade, none of those influences that promote the proper functions of the body, and tend to increase physical ease, should be neglected. For, if the brain is occupied with disagreeable sensations, it cannot concentrate its power as effectively in the various employments of man.