1 82 THE POPULAR SCIENCE MONTHLY 



THE NATURE OF FATIGUE 1 



By FREDERIC S. LEE, Ph.D. 



PROFESSOR OF PHYSIOLOGY IN COLUMBIA UNIVERSITY 



TO the conscientious schoolmaster the contemplation of a disserta- 

 tion on the nature of fatigue can hardly seem an unmixed joy; 

 for the subject is one with which he is already practically and sadly 

 familiar. I may say at once, however, that I have not come here to 

 remind you too acutely of this aspect of your professional work, your 

 sensations at the end of a busy day in the class room. I, too, have 

 felt those sensations, and I know how dully depressing, to both mind 

 and body, they may be. They must be reckoned with and eliminated 

 in the reform of the school. Much is written on the fatigue of the 

 school child, but the ideal school course will allow the teacher too to 

 bring an un jaded spirit to his successive tasks. In his Utopia the 

 teacher will have his playground, as the child now has his. My present 

 task, however, is not to limit myself to a discussion of the fatigue that 

 is incident to life in the schoolroom, but to present to you a study of a 

 specific topic in physiology, and to try to show that it lias broad biolog- 

 ical bearings. 



In popular usage the term fatigue is employed loosely, for while 

 it signifies, in general, a depression of physiological activity, resulting 

 strictly from previous activity, physiological depression is often called 

 fatigue when it is not at all clear that previous activity is at the 

 bottom of it. It does not, however, appear to me at present necessary 

 to hold always to the strict significance of the word, since in a given 

 case there are still too many unknown causative factors. Moreover, in 

 the marvelously complex weft of the human organism, where the 

 physical and the psychical are inextricably intermingled, illusion is so 

 readily mistaken for reality, especially in the phenomenon now before 

 us, as often to make the detection of a genuine fatigue well-nigh im- 

 possible. 



Let me proceed at once to an analysis of the phenomenon of fatigue. 

 Every one is familiar with its sensations; but not every one realizes 

 that the sensations are but signs of physical and chemical conditions 

 permeating the whole body. Fatigue is a general physiological phe- 

 nomenon; not only is the whole body subject to it, but every organ, tis- 

 sue and cell of which the body is composed. Like other general 

 physiological phenomena, its study may be best approached by con- 

 sidering its manifestations in the parts of the organism. I propose to 



1 An address delivered before the Section on Hygiene of the Connecticut 

 State Teachers' Association, at New Haven and Hartford. October 22. 1909. 



