148 



MOVEMENT 



from the spiral reached the registering tambour by- 

 means of a tube. 



In most acts of human locomotion muscular force 

 manifests itself in the form of pressure ; for instance, 

 this is the case when a man extends his legs from a 

 previous position of flexion ; as the legs become ex- 

 tended, the body mass is repelled in an opposite direc- 

 tion, because the feet, resting on the ground, offer a 

 fixed point of resistance. 



In walking or running, the foot presses on the ground 



Fig. 99 —Traction dynamograpb. 



with a force equal to that which is expended in moving 

 the body, so that by measuring at any moment the 

 pressure of the feet on the ground, we also measure 

 the force expended on locomotion. Our spiral dynamo- 

 graph is a useful instrument for this purpose. 



Dynamographic Platform for Registering the Pressure 

 of the Feet on the Ground. — A series of spirals, similar 

 to those previously described, are arranged on an oak 

 platform (Fig. 100). One of these spirals is left 



applied, and that this economy might even amount to 26 per cent, ot 

 the total motive force (JMarey, Trav. du Lalioratoire, I87r>). Wiist 

 found in similar experiments a saving of 22 to 33 per cent, in the 

 work. Kingelmann has noticed an economy in work amounting to 

 something like 50 per cent. 



