YIELD OF THE HUMAN MACHINE 193 



Atwater and Benedict ( l ) first thought of having a weight (a 

 block of iron of 5-7 kg.) lifted by means of a cord passing over 

 a pulley, and pulled by the arms. They had to abandon this 

 idea, because the work of the arms would have been unequal, 

 and also because of the negative work in the restrained descent 

 which cannot be accurately measured. 



By lifting weights to a certain height and letting them fall again 

 Hanriot and Richet ( 2 ) calculated R = 16% approximately, 

 from the measurements of the exchanges of gas, but without great 

 experimental accuracy. 



Laulanie ( 3 ) made some experiments, unfortunately of too 

 short duration, on the working by the arms of a special brake. 

 In trials lasting from two to five minutes, and for work done 

 amounting to 560 to 1660 kilogrammetres, he found the net 

 yield R to be 21 to 23% (see 121). 



Armand Gautier ( 4 ) estimated the dynamic expenditure from 

 the maintenance ration, on workmen employed in wine ware- 

 houses in the south of France, working ten hours a day at pumping 

 water. A vat (holding 15,000 litres) had to be filled, the water 

 being raised to a height of 10 metres, i.e. : 



T = 15,000 X 10 = 150,000 kilogrammetres. 



The minor supplementary work was estimated at 10,000 kilo- 

 grammetres. Hence : 



D, = 2,643 Cal., D, + D d = 4,218 Cal. in 24 hours. 



Consequently : 



160,000 _ 160,000 



" 425 (4,2182,643)" " 425 x 4,218 " 



This hard and continuous work causes many losses (such as 

 the friction on the handle, losses in the pump, and the raising of 

 the upper half of the body about 1,200 times) which Gautier 

 estimated at 100,000 kilogrammetres. 



Finally, Heinemann ( 5 ) gives 



R = 22-6% 

 for the muscles of the arms. 



137. Variations of the Yield. Chauveau's experiments have 

 shown the influence of speed and load on the amount of expendi- 



( x ) Atwater, Benedict and Woods (Bulletin, No. 44, p. 51, 1897). 

 ( a ) Hanriot and Richet (Comptes Rendus Sciences, vol. cv., p. 78). 

 ( 3 ) Laulani6, Trait de Physiologie, pp. 792, 801, 803, Paris, 1905. 

 (*) A. Gautier, L' Alimentation et les Regimes, Paris, 1908. 

 ( 6 ) Heineman (Pfluger's Archiv., vol. Ixxxiii., p. 441, 1901). 



