40 



ENERGY TRANSFORMATIONS DURING HORIZONTAL WALKING. 



which, in principle, was much like that used by him in studying; mus- 

 cular work done with the foot. 1 



This apparatus, shown in figure 6, consists of a small pointer A, 

 traveling on a brass block between two upright guides. The cord G, 

 attached to the pointer, passes over a pulley to the belt of the subject, 

 as shown in figure 1. The spiral spring F, previously referred to 

 in the description of the step-counter, keeps a tension upon the cord. 

 Obviously as the body is raised the tension of the spiral spring draws 

 the pointer down and as the body is lowered the cord draws the pointer 

 up. Each upward and downward movement of the body may be 

 recorded on a rotating kymograph drum, thus giving a graphic record 

 of the character of each step. A typical record is given in figure 7. 



It can be seen that the height to which the body is lifted may be 

 obtained from the kymograph record by measuring each downward 

 stroke of the pointer and adding the sum of the 

 values. Experimental conditions prevented us 

 from using a kymograph with a rapidly rotating 

 drum or a long paper kymograph, and the con- 

 sequent superimposing of the records shown in 

 figure 7 obviously makes the counting of the 

 number of steps somewhat difficult; neverthe- 

 less it is possible and has been done in a number 

 of instances (see table 2). By measuring several 

 points in the curve, an approximate average 

 height of step may easily be obtained; these 

 averages may then be multiplied by the total 

 number of steps recorded on the step-counter 

 and the distance to which the body is raised 

 computed. 



In an attempt to sum up these upward move- 

 ments by means of some automatic arrangement, 

 a special form of work adder-wheel was devised 

 for the purpose. This work adder-wheel, which 

 is shown as B in figure 6, relied upon the friction 



FIG. 6. Apparatus for recording the height to which the body is 

 lifted, and step-counter with connections. 



The cord G, connected with the body of the subject, passes over a 

 grooved wheel B attached to the shaft of a revolution-counter 

 C, a pawl p, preventing backward motion. It then passes 

 to a pointer A (the marker of Dr. Carl Tigerstedt), tension 

 being supplied by the light spring F. An upright cord 

 travels over a grooved pulley on the step-counter D, with the 

 tension produced by the small weight traveling in a tube E. 

 The height to which the body is raised at each step is thus 

 recorded in a dual manner, first, by the excursions of the 

 pointer A over a kymograph drum and second by the accumu- 

 lated movement of the wheel B. 



'C. Tigerstedt, Skand. Archiv f. Physiol., 1913, 30, p. 299. 



