ence in the circulation of the fatigue stuff produced by the exhausted muscles, or other nerve centers, although this is undoubtedly an element. If we call this will fatigue, it then becomes of importance to find the point in the training of the muscular system at which the maximum benefit to the physical organism can be secured without appreciably lessening the power of the individual, as shown by his willing ability. To use a less technical illustration: I may direct my mind to mathematics until it is fatigued; I may then turn to philosophy, and then to music, and so forth, but before all the abilities of the mind have been exhausted there is the fatigue of something that is back of all this. One may call it fatigue of the attention, or of the will, or, with Marie de Manaceine, a fatigue of the consciousness.
Most of us know in a practical way that there is such a thing as fatigue of the emotions. The relationships of these forms of fatigue to neuro-muscular fatigue will give us important light upon the subject of educational gymnastics. We have one evidence that these forms of fatigue are cerebral, even if not psychical—the fact that when muscles are operated by automatic centers the amount of expenditure can be vastly increased without fatigue—but when the consciousness must come in and either enforce or inhibit or alter in any way the automatic process, fatigue is greatly accelerated.
4. Muscular exercise is definitely related to the hygiene of the brain. That part of the nervous system that has to do with the control of the circulation of blood—the vaso-motor system—has been characterized as "the hub about which organic life revolves." It is certainly true that whether in the domain of intellect, feelings, or will, alterations in the circulation of the blood in the brain as a whole or as parts, and in the circulation of the blood in the viscera, are made. Our higher faculties appear to be related, not only to the brain, but to the sympathetic nervous system, having to do with the vaso-motor apparatus. The facts have been established that it is only in connection with exercise that the whole circulatory apparatus, as well as the vaso-motor system, comes to its full development. The balanced distribution of the blood to the body is definitely related to the power and regularity of the heart, and to that vaso-motor education that comes in connection with varied muscular contraction. In this field, empirical knowledge has gone far ahead of scientific investigations.
There are, however, simpler aspects of the relation of muscular exercise to the brain hygiene. The quality of the blood is directly affected by exercise and breathing. Deep breathing is promoted by exercise. The demand for oxygen and its supply in the system are both increased by oxygen. The power of the heart, and the healthy
