METHODS OF RECORDING MOVEMENTS. 



265 



writing- 

 tracings 



for their study a similar piece of apparatus lias 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 

 levers arranged in vertical series. The 

 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 



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. 



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 Muybridge, 

 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. — Alter 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. 

 bee also Londe, " La photo. meU," Paris, 1893. 



