METHODS OF RECORDING MOVEMENTS. 



265 



FIG. 153. Special appar- 

 atus for recording the 

 contacts of a horse's feet 

 with the ground ; a 

 transmitting tube effects 

 a communication be- 

 tween the air-chamber 

 and the chronographic 

 tambour. After 

 Marey. 



for their study a similar piece of apparatus has been used by Marey (Fig. 153). 



Indiarubber bags, stuffed with hair, are fixed in the hollow of the hoof, com- 

 municating, by means of a long indiarubber tube, 



each with a writing - lever. The rider (Fig. 154) 



carries a revolving drum, with the four writing- 

 levers arranged in vertical series. The tracings 



obtained from a man running are shown in Fig. 155. 



The continuous curve is that of the right foot, while 



the discontinuous curve is that of the left. The upper 



curve represents the oscillations of the centre of 



gravity. In both cases, descent of the lever is due 



to pressure of the foot upon the ground. Ascent is 



due to the sole of the foot leaving the ground. Marey 



usually represents his results directly obtained by 



means of the above curves in the notation seen on 



the lower part of this figure and in figure 156. The 



method of its derivation from the curves will readily 



be understood by reference to figure 155. 



Vierordt modified Marey's method, using electrical 



recorders instead of air recorders. In other experi- 

 ments, tiny outflow pipes from a reservoir of coloured 



fluid, carried on the shoulders of the runner or 



walker, were attached at various points, such as 



the -hip, knee, shoulder, etc. From these outflow 



pipes a continuous flow spurted upon a piece of 



paper, fixed vertically by the side of the person 



under observation, and thus recorded the movements which were taking 



place. 



Chronophotographic method. This method is a modern one, dating 



from the year 1878, when Janssen took a series of photographs of the 



planet Venus while 

 it was traversing 

 the sun's disc, and 

 suggested a similar 

 method for the in- 

 vestigation of animal 

 locomotion. It has 

 since been used with 

 remarkable success 

 by M u y b r i d g e, 

 Marey, Anschiitz, 

 Braune, and Fischer. 

 Muybridge, in 

 studying the move- 

 ments of the horse, 

 caused that animal 

 to run in front of a 

 white screen along 

 a track across which 

 were stretched a 

 series of wires, each 

 one of which formed 



FIG. 



154. The chronographic apparatus for recording the 

 paces of a horse. After Marey. 



part of the circuit of an electro-magnet, which closed the shutter of a photo- 

 graphic camera. When the horse broke the wires, one by one, a shutter 

 was released each time, and the horse was photographed. 1 



1 "The Horse in Motion, as shown by Instantaneous Photography," London, 1882. 

 See also Londe, " La photo, me'd.," Paris, 1893. 



