METHODS OF MEASUREMENT. 31 



nected to the shaft of a revolution-counter, and a record of the total 

 movement of the wheel was thus obtained. The total distance the 

 body was raised would theoretically be that found by multiplying the 

 number of revolutions of the wheel by its circumference. These read- 

 ings were made for 10 minutes during every period 12 or 13 ruinates in 

 length. 



Another change in the procedure was the use of ink in place of 

 smoked-paper tracings on the kymograph drum. The speed of the 

 kymograph was regulated to one complete revolution in 3 minutes. If 

 a lower speed than this was used, the tracings of the pen were frequently 

 superimposed upon one another, making it difficult to distinguish the 

 individual steps. As it was necessary to readjust the kymograph 

 between the end of each revolution and the beginning of the next one, 

 only three 3-minute tracings could be obtained during the period. The 

 average of these three 3-minute records was taken as the average 

 elevation of the body per minute during the entire period of 12 or 13 

 minutes. The tracings upon the kymograph-drum were used, how- 

 ever, simply to check the records of the step-lift counter in case it failed 

 to act properly. 



A criticism 1 has recently appeared of the method used by Benedict 

 and Murschhauser 2 in measuring the step-lift, to the effect that, in 

 walking, their subject changed his position on the treadmill, thus 

 changing the length of the cord from his back to the pulley from which 

 the cord ran to the kymograph. Since the criticism would apply to 

 some extent to the method used in this research for measuring the step- 

 lift, several experiments to test this point were made on a subject not 

 used in the research of Benedict and Murschhauser, as neither of these 

 was available. 



A small incandescent lamp was inclosed in a tin can with a hole in it 

 through which the light would shine. One of these lamps was fastened 

 to the back of a subject at the point of attachment used by Benedict 

 and Murschhauser (the waist-line) and a second light to the point 

 between the shoulders used in the present research. For a scale of 

 measurement, two lights, 1 meter apart, were affixed to a board centered 

 in the same plane and behind the subject. Photographs were then 

 taken of the movements of the spots of light at the waist and shoulders, 

 respectively, during the cycle of one double step when the subject was 

 walking on a level and on grades of approximately 10 and 25 per cent, 

 with a speed in each case of 71 to 74 meters per minute. These photo- 

 graphic records were made not only with the camera stationary, but 

 also with the camera rotated, so that tracings were obtained across the 

 full length of the photographic plate. 



By measuring the spacing of the light spots on the photographic 



'Liljestrand and Stenstrom, Skand. Arch. f. PhysioL, 1920, 39, p. 167. 

 'Benedict and Murschhauser, Carnegie Inst. Wash. Pub. No. 231, 1915, p. 39. 



