796 POPULAR SCIENCE MONTHLY. 



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 sub- 

 ject 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 ex- 

 penditure can be vastly increased without fatigue — but when the con- 

 sciousness 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 con- 

 trol 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 educa- 

 tion that comes in connection with varied muscular contraction. In 

 this field, empirical knowledge has gone far ahead of scientific inves- 

 tigations. 



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 



