THE NATURE OF FATIGUE 191 



of fatigue result largely from events happening outside of the brain 

 and spinal cord, events of which 1 have been speaking under the 

 head of physical and chemical phenomena. Such events are not, how- 

 ever, confined to the particular tissues that have performed the fa- 

 tiguing work, for fatigue substances, though produced in one tissue 

 and fatiguing it, may be carried by the blood to others and there also 

 exert their characteristic action. This fact, that the excessive work of 

 one tissue may cause the fatigue of other tissues, is of great practical 

 importance to us in our daily life. We all believe that excessive muscu- 

 lar work may cause mental weariness. It has been shown by laboratory 

 experimentation that the reverse is true, that excessive mental work 

 may cause muscular weariness. In an experiment upon himself Dr. 

 Maggiora, of Turin, found that the flexor muscles of his middle finger, 

 upon being stimulated by an electric current applied directly to them, 

 were capable of lifting a certain weight fifty-three times before temporary 

 exhaustion set in (Tig. 6). Soon after the completion of the test he en- 

 tered the class room and devoted the subsequent three and one half hours 

 to the oral examination of students, a task which, he being then a teacher 

 of little experience, was excessively difficult. Immediately after the 

 end of the examination he tested his lifting power again and found his 

 muscles capable of making only twelve contractions. It is often 

 thought that the best means of recuperating after a day's hard mental 

 labor is through the performance of physical exercise. A temporary 

 change of occupation may, indeed, be of great benefit, by relieving an 

 exhausted organ and an exhausted focus of attention. But physiology 

 tells us that a tired brain means a tired body, and that with the brain 

 fagged there is nothing culpable in a desire for not only mental but 

 physical rest. 



But there is another aspect of personal fatigue which we can not 

 neglect. Our sensations become our servants or our masters, accord- 

 ing as we will. Either we control them, or they control us. Is it 

 legitimate, is it moral, to yield to every sign of weariness? Here we 

 meet at once the problem of the formation of habits. Fatigue may 

 easily become with us a habit, a habit which is destructive to legitimate 

 effort. We have all known the perpetually tired man, the chronically 

 fatigued, to whom both initiative and performance alike are distasteful 

 and to be avoided, when possible. This condition may at times be so 

 pronounced as to be positively pathological, demanding special curative 

 treatment. Fortunately such a condition is rare. Most of us may 

 live on a high or a low plane of activity at will; we may do much or 

 little ; we may yield early to fatigue or we may successfully resist it for 

 a time with impunity. 



The more one studies physiology the more one appreciates the fact 

 that protoplasm possesses an enormous power of work, and that the 

 human body is endowed with marvelous capacity. Whether we shall 



