tATlGUE. 479 



Fatigue. By William McDougall, M.A., M.B. 



[Ordered by the General Committee to be printed in extenso.'] 



The study of fatigue must always be of the deepest interest from the 

 point of view of pure science, because in studying fatigue we are study- 

 ing the sources of human energies, the modes and conditions of their 

 operations, and, above all, their limitations. But the general speeding up 

 of life, which is the most striking characteristic of modern civilisation, 

 and which affects all classes at all ages from early childhood onwards, 

 is rendering the study of the problems of fatigue a matter of the most 

 urgent practical importance, and the scientific world has not been slow 

 to recognise the fact. 



The physiologists of the laboratory have studied fatigue in its most 

 elementary manifestations, in the various organs and tissues, and at its 

 ultimate and secret source, the cell. The psychologists have devoted 

 much ingenuity to the study of the expeiiraentally induced fatigue of 

 the human organism as a whole, seeking specially to find means of 

 measuring the degrees of fatigue and their influence upon the efficiency 

 and the development of the various powers of mind and body. The 

 physicians have discovered in the chronic fatigues produced by modern 

 conditions of life the source of a large range of disorders which seem to 

 have been unknown to, or at any i-ate unrecognised by, our forefathers. 

 There is no ground on which the problems of mental and of bodily 

 processes are so intimately and inextricably bound up together. 

 There is no field of scientific research in which there is more need of 

 co-operation between the various classes of workers, the physiologists, 

 the medical men, the psychologists, and the sociologists ; there is no 

 biological problem in dealing with which it is more necessary to keep in 

 mind both the organ and the organism in all their aspects. 



On an occasion of this kind it is, I think, proper that we should 

 attempt to effect some synthesis, some fruitful combination of the con- 

 clusions and the hypotheses indicated by the work done along these 

 different lines. I shall hope, therefore, for your indulgence if I venture 

 to offer you one or two speculative suggestions as contributions towards 

 such a synthesis, suggestions whose only justification must be the degree 

 of success with which they enable us to occupy the more comprehensive 

 view-point in face of the problems of fatigue. 



Our English word ' fatigue ' is a most comprehensive one. Wherever 

 there is evidence that organic activity results in diminished capacity of 

 the organism to carry on any of its functions, there we commonly 

 recognise fatigue. 



Of all the manifestations of fatigue the most familiar are the subjective ; 

 of these subjective symptoms we must distinguish at least three classes : — 



(1) Local sensations of fatigue, more especially in the muscles. 



(2) The sense of feeling of general tiredness, of limpness, and general 

 incapacity for eff"ort. 



(3) The experience we call sleepiness. 



The first of these I want to dismiss with a single observation. You 

 may get this sensation of local fatigue in the acutest form by holding out 

 a limb— say the arm — for a few minutes against the pull of gravity. 



