INFLUENCE OF WORK 501 



Observations made by Gruber and Schnyder upon man show 

 that the output of carbon dioxide for the performance of a definite 

 piece of work can be reduced by practice to two-thirds of the 

 original value ; this is also proved by the results obtained by Zuntz 

 and Schumburg ( 12 ) in the case of recruits and trained soldiers. 

 The recruit learning to march at first uses more muscles than are 

 necessary, and works uneconomically even the ones which are 

 necessary for the movements ; during any given march he dis- 

 charges a larger amount of carbon dioxide than he will do after 

 training. 



Fatigue is also accompanied by an extravagant metabolism ; 

 from this cause the output of carbon dioxide may be increased 

 even as much as 21 per cent. An abnormal rise in the temperature 

 of the body is produced by excessive and prolonged work under 

 unfavourable conditions, and apparently causes a further extrava- 

 gant combustion. 



Soreness of feet caused by unsuitable boots will cause the 

 sufferer to bring into action muscles other than the usual ones 

 required for walking ; this he does, even unconsciously, in order 

 to diminish as far as possible the movement or pressure which 

 causes pain. The abnormal use of such muscles causes an 

 extravagant combustion and more fatigue. Soldiers in such a 

 plight are often forced to fall out of the ranks, especially if they 

 have been marching rapidly in unsuitable clothes, exposed to a 

 hot and moist atmosphere and loaded with rifle, ammunition, 

 and kit. The combined action of these unfavourable conditions 

 will in many cases cause such an abnormal rise in the temperature 

 of the body that " heat stroke " is the result. Work which is 

 performed painfully by man or beast is uneconomical. The truth 

 of these statements has been fully demonstrated by the successes 

 and failures of forced marches. Pain is beneficent ; it is a warning, 

 a natural safeguard, an incentive to rest ; the sensations of pain 

 may be neglected, or may be deadened by drugs and work can be 

 performed, but it is extravagant work, and the penalty has to 

 be paid sooner or later. 



An examination of the respiratory and nitrogenous exchange 

 indicates that muscular work is performed without any actual 

 destruction of the proteid of the muscles. The carbohydrate 

 moiety of the complex proteid molecule appears to be split off, 

 and to yield on combustion the energy and heat of muscular con- 



