298 



THE HUMAN MOTOR 



At each flexion of the finger, a curve is registered whose ordinate 

 expresses the displacement / of the weight P ; the motor work 

 done by contraction is therefore P X /. The intensity of the 

 contractions becomes progressively less because of the fatigue, 

 and the general trend of the curves is descendant, especially when 

 the rhythm of the movements is accelerated. The whole of the 

 contractions registered up to the point of fatigue is called an 

 ergogram. Fig. 142 shows a few ergograms. 



223. Various Ergographs (on Mosso's Principle). There are a 

 considerable number of ergographs having the same principle as 

 that of Mosso. Most experimentalists have used the mesial 

 finger for their experiments, ( l ) except Storey, ( 2 ) who, noticing 

 the constraint of this finger when the others were immobilised 

 by the apparatus, used the index finger ; this is certainly more 

 normal. 



Treves designed a brachial ergograph,( 3 ) shown in fig. 211. 

 The subject leans 

 against a vertical 

 wall A, whilst his 

 right arm is fixed in 

 a saddle, B, by 

 means of a strap. A 

 bracelet, G, attaches 

 the forearm to the 

 crank-handle E, of a 

 wheel C, whose axis 

 lies in the prolonga- 

 tion of the transverse 

 axis of the elbow 

 joint. The weight P 

 to be lifted is sus- 

 pended from a cord 

 which runs in the 

 groove of the wheel 

 C. Finally from the 

 axle H of the latter, 

 a cord runs to the Troves brachial ergograph. 



inscribing slide. 



To obtain the value of the work done, the radii R of the crank 

 handle, r of the wheel, and r' of the axle, must be taken into 



( 1 ) Lombard (Journ. of Physiol. vol. xiii. pp. 1-58 1892) ; Pantanetti, 

 (Arch. Ital. Biol., vol. xxii., p. 17, 1898) ; Troves, (Ibid., vol. xxxvi., p. 44, 

 1901) ; Binet and Vaschide (Annie Psychol., 1898, p. 303) ; Grandis (Arch. 

 Sc. Med. vol. xxvi. p. 269, 1902). 



( 2 ) Storey (Amer. Journ. of Physiol. vol. viii., p. 355, 1903. 

 () Treves (Arch. Sc. Med., vol. xxii., p. 373, 1898). 



