134 MOVEMENT 



place in three directions of space, and thus require 

 simultaneous registration by three curves. 



Nevertheless, our late pupil and friend, Carle t,* 

 obtained, by the geometrical combination of three 

 curves recorded simultaneously, the actual path 

 described by a selected point on the body of a man 

 walking. A movement of this nature can only be 

 represented by a solid figure. 



Carlet used for this purpose a piece of wire twisted 

 in different directions. A flat figure, even with the 

 help of light and shade (Fig. 91), can only give a very 

 imperfect representation of a movement of this kind. 



Fig. 91. — The trajectory of the pubis of a man at a walking pace. A metal wire 

 twisted in various ways indicates the variations of this curve in respect to the 

 three directions of space. 



►Stereoscopic images alone are capable of giving a 

 satisfactory picture of it. Now, we said in Chapter II. 

 how easily images of this kind might be obtained. 

 Fig. 14 shows a trajectory very similar to that 

 laboriously obtained by Carlet. 



AVhen it is a matter of registering all the details 

 of a man's movements, both as regards change of 

 position and attitude of the body and limbs, mechanical 

 registration is out of the question. It is at this point 

 that chronophotography comes to the rescue. 



The Study of Movements in Man by means of Chrono- 

 photography on Fixed Plates. — In Chapter II. we 

 showed how to obtain on -fixed plates a series of images 

 corresponding to the successive phases of a movement, 



* Carlet, " Essai Experimental sur la Locomotion de 1' Homme," 

 Annates des Science* \aturelles, 1872. 



