294 



THE HUMAN MOTOR 



which closes a metal case C. A strong 

 iron casing carries the rings A and B. 

 The resistance to be displaced acts at 

 B and the effort is exerted at A raising 

 the membrane slightly and producing 

 a rush of air which acts on a receiving 

 tambour (fig. 202) . The graph will give 

 the value in kilogrammes of the efforts 

 of traction. The rotation of the pulley 

 is transmitted by a system of reduction 

 to the registering cylinder and, as a 

 result, the area of the curve described 

 gives the amount of work done. The 

 distances covered can be reduced by 

 combinations of gears or by pulleys of 

 different diameters as required. Marey 

 verified that the amount of work re- 

 quired to lift a load is greater than 

 that for lowering it. 



221. Ergometric Apparatus. Laul- 

 lanie's dynamometer is as follows ( l ) ; 

 Around the groove of a large pulley a 

 metal strap passes, with equal weights, 



FIG -202 

 Marey's dynamograph. 



Fie. 203. 

 Laulani6's weight brake. 



P and P' at either 

 extremity. The weight P is attached to 

 a special weighing machine p (fig. 203). 

 The subject turns the pulley at a constant 

 speed. The work done is equal to the 

 product of 2rm (n == number of revolu- 

 tions) by the friction indicated on the 

 dial of the weighing machine. This 

 apparatus was used for measuring work 

 done by the arms. Atwater and Bene- 

 dict ( 2 ) used an ergometric bicycle whose 

 arrangement was such that the whole 

 of the friction was converted into heat 



in a calorimetric chamber and was thus measured. This appar- 

 atus cannot therefore be used independently of a calorimetric 

 installation. The reader interested in this technique can refer 

 to the original memoir (see 103). 



The ergometric bicycle ( 3 ) can be more simply and correctly 

 employed as follows : A bicycle is mounted on a rigid frame 

 (fag. J04), the back wheel being weighted and well balanced so as 



(|) Laulanie" (Comptes Rendus Biologic , 1903, p. 880) 



iQn^ At ^ at D r f, nd Benedict (Bulletin, No. 136, p. 30, 1903 ; No. 208, p. 11, 

 1909) and Publication No. 167, 1912). 



H Jules Amar (Journ. de Physiol., 1912, p. 303). Cf. Le Rendement de 

 la Machine Humaine p. 30, Paris, 1910. 



