38 



ENERGY TRANSFORMATIONS DURING HORIZONTAL WALKING. 



surface of the leather belt. As one end of the chain brush was grounded 

 to the brass tube, when the ends of the chain dragged over the surface 

 of the revolving belt the stray electric currents were picked up and 

 grounded. Satisfactory records could thus be obtained. Unfor- 

 tunately the conditions of the experimental work in the Laboratory 

 at that time prevented our freeing a galvanometer and oscillograph 

 for the particular purpose of determining the pulse-rate; consequently 

 records could not be regularly secured. Indeed, the few observations 

 obtained were of so striking a character that we can not adequately 

 discuss them in this monograph. 1 



STEP COUNTER. 



With a steady electric current, the rate of revolution of the treadmill 

 per minute is presumably fairly constant and the length of the steps 

 in ordinary walking is also doubtless approximately the same ; neverthe- 

 less it is important to show in these tests the exact number of steps 

 -taken, so as to indicate the distance per step and thus furnish an added 

 factor for analyzing the mechanics and physiology of walking. To 

 count the steps automatically was imperative, as even with several 

 assistants an accurate record of the steps during exceedingly rapid 



FIG. 4. 



FIG. 5. 



FIG. 4. Detail of ball bearing for steel tubes on the treadmill. 



FIG. 5. Step counter. A pulley A is attached to the extended shaft of a revolution counter; 

 a small cord passes over this pulley and is protected by a guard C. The shaft automat- 

 ically stops at B and B'. 



walking would be very difficult to obtain. A small device was there- 

 fore employed which counted automatically each vertical motion of 

 the body produced in walking. 



To a belt about the waist of the subject was attached a cord leading 

 over two pulleys on the ceiling to a small spring which maintained 

 a tension on the cord. The general arrangement of this device is shown 

 in figure 1 and the details in figures 5 and 6. At each step the sub- 

 ject lifted the body a certain distance and lowered it again. Advan- 

 tage was taken of this lifting and lowering of the body to raise and lower 

 a small weight (E, fig. 6) at the end of a cord which rested upon a pulley 

 (A, fig. 5, and D, fig. 6) on the shaft of a revolution counter (see fig. 5). 



'See pp. 85 and 92. 



