168 SECTIONAL ADDRESSES. 



has a whole series of protective mechanisms at its command, an 

 organism wliich can be fatigued and rendered useless, as a working 

 unit, by an amount of work on a particular day which on another day 

 it can perform with the utmost ease and without apparent fatigue. 

 We are dealing with an organism which can and does perfonn real 

 hard muscular work with vigour and joy, and yet, if the nature of the 

 employment or the environment be distasteful, can be reduced to 

 impotence by work capable of being done by a child. 



Again, the efficiency of a man is not merely dependent on the 

 amount of work which can be performed by his muscles; the circulatory, 

 respiratory, and nervous systems are of equal importance, and all are 

 intimately related. The muscles must receive an abundant supply of 

 blood, not merely to bring nutriment but to remove waste ; there must 

 be an efficient exchange of gases in the lungs, the rate of the respiratory 

 and cardiac movements must be adapted to the work in hand through 

 the co-ordinating agency of the central nervous system. Not only so, 

 but, if the man is to work with the minimum of waste energy, there 

 must be proper co-ordination between the various gi-oups of muscles. 

 A man does not walk, for instance, by the aid of his leg muscles alone, 

 his lumbar muscles are equally important. Further, it is not a mere 

 question of autonomic reflex adjustment, important though this may 

 be, for much of the work done the attention must also be invoked. 

 Yet, in spite of the many and varied stresses and strains to which the 

 organism is subjected in the course of life, as the result of the many 

 factors of safety, unless the overloading is excessive, too frequent or 

 too long continued, the organism, so long as it remains physiological, 

 is practically unaffected by ordinary hard work. 



If we turn now to the consideration of the factors which influence 

 the efiiciency, both in the mechanical and the industrial sense, we find 

 that the main controlling factor is undoubtedly the condition known as 

 fatigue. Fatigue is a word just as frequently used as efficiency, and 

 yet it is almost impossible to give an accurate definition of the term. 

 Generally speaking, it is to be regarded as the antithesis O'f efficiency. 

 As Vernon put it, ' By so much as fatigue is avoided or eliminated in 

 industrial operations the efficiency of the worker is increased. ' 

 Fatigue may be summarised as a diminished capacity for doing work. 

 The question of the site at which fatigue is first manifested, whether 

 it is a central oi' a peripheral phenomenon, whether it is a specific con- 

 dition, or whether, as Crile maintains, there is no ultimate difference 

 between the bloodless intangible causes of fatigue and exhaustion and 

 the bloody tangible causes of ' shock, ' lies without the scope of this 

 address. One of the great difficulties in the solution of the question is 

 that no one has as yet devised a method which permits of a quantitative 

 determination of the degi'ee of fatigue. Indeed, some workers, Muscio 

 for example, have definitely stated that such a test is an impossibility. 



The study of the metabolism has given little or no clue so far. 

 Benedict and I carried out a certain amount of experimental work on 

 this phase of the question. Our results show that the subject may be 

 on the very verge of absolute collapse, and yet, so far as the metabolic 

 determination goes, there is no very marked evidence of diminished 



