"A second change in fatigue has been found in the cell body of the neurone. Hodge showed that the size of the nucleus of the cell in the spinal cord of a bee diminished nearly 75 per cent, as a result of the day's activity, and that the nucleus became much less solid. A third change that has been demonstrated as a result of muscular work is the accumulation of waste products in the muscle tissue. Fatigued muscles contain considerable percentages of these products. That they are important factors in the fatigue process has been shown by washing them from a fatigued muscle. As a result the muscle gains new capacity for work. The experiments are performed on the muscles of a frog that have been cut from the body and fatigued by electrical stimulation. When they will no longer respond, their sensitivity may be renewed by washing them in dilute alcohol or in a weak salt solution that will dissolve the products of fatigue. It is probable that these products stimulate the sense-organs in the muscles and thus give some of the sensations of fatigue. Of these physical effects of fatigue, the accumulation of waste products in the blood and the effects upon the nerve cells are probably common both to mental and physical fatigue. The effect upon the muscles plays a part in mental fatigue only so far as all mental work involves some muscular activity." By this time you must be convinced that the subject of fatigue is exceedingly complicated; that its effects are manifested differently in mind and body. In relieving fatigue the first step to be taken is to rest properly. Man cannot work incessantly; he must rest sometimes, and it is just as important to know how to rest efficiently as to know how to work efficiently. By this is not meant that one should rest as soon as fatigue begins to be felt. Quite the reverse. Keep on working all the harder if you wish the second-wind to appear. Perhaps two hours will exhaust your first supply of energy and will leave you greatly fatigued. Do not give up at this time, however. Push yourself farther in order to uncover the second layer of energy. Before entering upon this, however, it will be possible to secure some advantage by resting for about fifteen minutes. Do not rest longer than this, or you may lose the momentum already secured and your two hours will have gone for naught. If one indulges in too long a rest, the energy seems to run down and more effort is required to work it up again than was originally expended. It is also important to observe the proper mental conditions during rest. Do not spend the fifteen minutes in getting interested in some other object; for that will leave distracting ideas in the mind which will persist when you resume work. Make the rest a time of physical and mental relief. Move cramped muscles, rest your eyes and let your thoughts idly wander; then come back to work in ten or fifteen minutes and you will be amazed at the refreshed feeling with