116 



PHYSIOLOGY 



CHAP. 



walk past a black ground with a white net on his back which is vividly 

 illuminated by direct sunlight. While he walks a rotating apparatus lets 

 light into the camera obscura at regular intervals. At each instantaneous 

 exposure an image of the subject in different postures is thrown upon the 

 successive parts of the plate (Figs. 82 and 84). In order to obtain more 

 images at each cycle, and at the same time to avoid the confusion resulting 

 from their superposition, Marey invented the ingenious method of partial 



Km. 7-j. Curve of walking. (Marry.) />, movements of right foot ; 5, of left foot ; 



II, vertical oscillations. 



which consists in suppressing the images of the left side of 

 the body, photographing only the right half of the walker. For this 

 purpose the left half is clothed in black, the right in white (Fig. 76). 

 The figures of each step can similarly be multiplied in walking or run- 

 ning by increased simplification of the images. For this the subject is 

 clothed entirely in black, six brilliant metal buttons being placed on the 

 head and over the articulations of the shoulder, elbow, thigh, knee, and foot, as 

 well as five shining bands over the bone of the arm, forearm, thigh, leg, 

 and edge of the foot (Fig. 77). By photographing the subject as he walks 

 forward strongly illuminated by the sun, the chronophotogram is obtained, 

 as shown in Fig. 78, where, for the sake of simplification, the tracing of the 



Fiii. 76. Photographs of right half of body of a subject walking slowly iiasl the camera. (Marey.) 



head is omitted, since it shows only vertical oscillations which are perfectly 

 comparable at every step with those of the dots on the shoulder and thigh, 

 as shown on the figure. 



A later improvement on Marey's method was introduced by Braune and 

 Fischer, who substituted for the dots and metal bands on the black coat of 

 the subject, upright Geissler's tubes, connected with the conducting wires 

 of a circuit which included a big Ruhmkorf induction apparatus. The 

 circuit was interrupted at equal intervals, which lasted O0383 parts of a 

 second. By photographing the subject as he w r alked not only along a plane 

 parallel with the sensitive plate but also along other planes, Fischer was 



