282 



THE HUMAN MOTOR 



handles. Two metal laths, PQ and P'Q'. are fixed across the 

 latter, and have two rings underneath, in which slide two strong 

 iron rods terminated by the handles I and I' (fig. 178). 



These two rods are riveted to a transverse metal rod, HL, 

 absolutely detached from the wooden handles, but to which 

 is attached one end of a strong spiral spring, R, the other end 



being fixed on the rod 

 P'Q'. Hence, when 

 holding the handles I 

 and I', the workman 

 will exert an effort on 

 /' the transverse rod HL, 

 whose displacements 

 will be limited by the 

 spring R. These dis 

 placements are trans- 

 lated by the deform- 

 ations of a small indiarubber bulb, c, 

 placed in a cup and in contact with a 

 small disc, d, contact being made by 

 the screw v. This arrangement is both 

 sensitive and accurate^ 1 ) 



212. Marey's Experimental Shoes. 



The effort exerted by the foot on^the 

 ground, on a 



178. 



Fio. 170. 



Shoe for measuring the 



pressure of the foot on 



the ground (Marey). 



pedal, and so 



forth, can be 



registered by 



fitting the 



shoes with appropriate tambours. 

 Marey's ( 2 ) model comprises a thick 

 indiarubber sole, inside which is a 

 small, hollow chamber. The fall and 

 rise of the foot give rise to an expan- 

 sion or compression of air which is 

 communicated to a receiving tympan. 

 When walking, the subject carrie 5 

 a small registering cylinder in his 

 hands (figs. 179 and 180). It should 

 be recognised that the air chamber 

 is not in contact with the entire 

 surface of the foot, and therefore on 

 this account the readings of the effort 

 produced are rather uncertain. Besides 

 which, this kind of footwear will not allow long walks. 



0) A. Imbert (Bull. Insp. Travail Nos. 1 and 2, 1909 ; separate reprint 

 pp. 8-9). 



() Marey, La Mithode Graphique pp. 155 and 497, 1878. 



Kio. 180. 



