Specialization in business not conducive to health
One may alternate from one kind of activity to another indefinitely, which would be better than no change, but the human mechanism would finally give way under such violation of fundamental law. The mental worker may change, however, to any manual labor requiring little thought, and the physical worker to some form of mental labor, with far better effect. But, in our present civilization, specialization has become so far advanced that the physical laborer is seldom qualified for mental work, and the mental worker has almost neglected manual training.
True rest and re-creation is found in mental tranquility and sleep.
SLEEP
From observation and study of the state we call sleep, we notice that as night approaches and the activities of the day wear upon us, both the nervous and the muscular organisms relax, so that it becomes more and more difficult to maintain a positive and an active attitude of mind. There is a tendency toward cessation and rest, which gradually brings upon us that passive condition called sleep.
Evidence of acquired energy during sleep
In spite of the fatigue often experienced before we retire, we awake again on the morrow with renewed strength and power. From these and other reasons we are led to believe that during the hours of activity the body is constantly expending vital energy in both internal and external work, and that during the hours of sleep, through some unknown process, the body is charged with vital energy which is stored up and used gradually for carrying on the various functions and activities of the system.
The mystery of energy
Just what this energy is, just where it comes from, just how it is stored, just the manner in which it is delegated to the body, we cannot say. We can only observe its workings, or effects, and formulate therefrom a theory. We are led to believe, however, that this energy is stored in the nervous organism, perhaps most largely in the brain, as brain tissue is the last to break down or waste away in sickness, ill health, dis-ease, or starvation, often maintaining its full weight up to the point of death.