406 THE HUMAN MOTOR 



Marey's system of graphic registration was employed. The 

 general principle of the experiments consisted in arrangements 

 by which the muscles of the hands acted on springs compressing 

 the same slightly. The pressure of the springs was transmitted 

 to small rubber bulbs, which latter were each connected to a 

 Marey's " tambour " (vide fig. 277). 



The amplitude of the movement of the stylus is so arranged 

 that legible charts can be obtained. The dynamographic arrange- 

 ments applied to the tool, and the work are those described in 

 para. 214 above. 



By this apparatus both the pressure of the left hand, V, and 

 the combined pressure of both hands, V + V, can be measured ; 

 hence the pressure of the right hand V, can be readily deduced. 



The horizontal components, H and H', are measured separ- 

 ately. 



The total weight of the file, complete with the dynamographic 

 fittings, was 1,850 grammes, which weight must be added to V -f- 

 V in our computations. 



The material on which the experiments were carried out was 

 a block of brass. 



The power needed to draw the file back over the work (vide 

 fig. 278) was found to be 550 grammes. The co-efficient of fric- 

 tion was therefore approximately : 



1-850 



Fit. 27* 



Measurement of power on the return stroke of a file. 



The workman stands at the vice, on a platform the height of 

 which can be adjusted. As will be seen later, this height, and 

 the consequent attitude of the workman, have an important 

 influence, both on the fatigue and the output of work. 



The expenditure of energy is measured by the consumption of 

 oxygen, using the thermal equivalent of a litre of oxygen. By 

 analysing the gases expired, at rest, and at work, respectively, 

 the additional consumption due to the work can be arrived at. , 



Also the respiratory quotient gives the calorific value of the 





additional consumption, in other words, the actual dynamic 

 expenditure. The respirations were recorded, graphically, sim- 



