730 



SCIENCE 



[N. S. Vol. XLIV. No. 1143 



the muscle contract more rapidly, in- 

 creases the degree of fatigue in a given 

 time and, if continued, brings on earlier 

 exhaustion. These facts have their counter- 

 part in industrial work, for fatigue here 

 too depends on the intensity and the ra- 

 pidity of repetition of the individual acts 

 performed by the laborer. In general it 

 may be said that the introduction of so- 

 called labor-saving machinery has dimin- 

 ished the intensity and increased the ra- 

 pidity of repetition of the laborer's acts. 

 Lifeless machines now often lift the heavy 

 weights once raised by human muscles. 

 Other lifeless machines, intricate and auto- 

 matic, relieve the laborer of much of his 

 former light muscular work. But these 

 same machines need to be tended by hu- 

 man agencies and set the pace for human 

 activities, and the tendency is ever toward 

 increasing the quickness and the constancy 

 with which sense-organs, brain, spinal cord, 

 and muscles must act. 



The introduction of periods of rest while 

 a laboratory experiment with a muscle is in 

 progress diminishes the fatigue of the 

 moment, aids recuperation, and delays the 

 oncoming of exhaustion. This is demon- 

 strated very perfectly in each of us several 

 times in a minute, since each beat of the 

 heart is followed immediately by a resting 

 period of sufficient length to enable the 

 cardiac muscle completely to recuperate 

 from the fatiguing effects of the previous 

 contraction. The beneficial effects of simi- 

 lar resting periods in industrial labor are 

 shown by the custom, not uncommon since 

 the striking demonstration of the late Mr. 

 Frederick Taylor in the lifting of heavy 

 iron pigs, of giving workers occasional 

 brief intervals of freedom from their tasks. 

 The defenders of the twelve-hour duration 

 of work in blast furnaces attempt to justify 

 their attitude by the contention that the 

 workman actually works but a fraction of 

 the whole time on duty. A timely and 



striking instance of the value of frequent 

 resting periods is reported by the British 

 Health of Munition "Workers Committee: 

 Two officers at the front recently, for a friendly 

 wager, competed in making equal lengths of a cer- 

 tain trench, each with an equal squad of men. One 

 let his men work as they pleased, but as hard as 

 possible. The other divided his men into three 

 sets, to work in rotation, each set digging their 

 hardest for five minutes and then resting for ten, 

 till their spell of labor came again. The latter 

 team won easily. 



Fatigue is modified by the external con- 

 ditions under which the work is performed. 

 Thus, it was found by Scott and myself 

 that when an animal had been exposed for 

 six hours to an atmosphere with a tempera- 

 ture of 91° F. (33° C.) and 90 per cent, 

 relative humidity the fatigue of the ani- 

 mal's muscles came on more rapidly and 

 their working power was diminished by 

 about one quarter. Certain industrial oc- 

 cupations too require their work to be per- 

 formed in the midst of excessive heat and 

 humidity and thus afford the conditions of 

 an early oncoming of fatigue and exhaus- 

 tion. Doubtless other environmental con- 

 ditions, such as excessive or deficient light, 

 noise, and gross mechanical vibrations, in- 

 fluence the fatigue process, but these have 

 not been adequately and experimentally 

 studied. Attention might here be called to 

 the suggestive little book recently published 

 by the Gilbreths, which shows by what easy 

 and simple means unnecessary fatigue may 

 often be avoided. 



It is obvious that if, under any given con- 

 ditions of intensity and rate of labor and 

 of its environmental features, the working- 

 day is of such a length as to bring about 

 the evil physiological results here men- 

 tioned, the surest way to avoid them is to 

 shorten it. There exist few, if any, stud- 

 ies devoted to the specific physiological ef- 

 fects of a reduction of the working-hours, 

 and this gap in our knowledge it is desir- 

 able to fill; but that the general health of 



