PHYSIOLOGICAL CHANGES IN TRANSITION. 303 



PULSE-RATE IN TRANSITION FBOM GRADE WALKING TO STANDING. 



The changes in the duration of the pulse-cycle occurring when the 

 subject stopped walking and stood are shown in curves D and E in 

 figure 41 and also in four curves in figure 42. Curve D in figure 41 

 represents the records obtained after the subject had stood 8 minutes. 

 Like curve C in the same figure, this record was made with the tune- 

 intervals lengthened by an increase in the speed of the paper through 

 the camera, and is thus largely free from errors of measurement. 

 During this record there was difficulty with the feed of the paper 

 at the points indicated by the broken lines, and the record is not 

 continuous for 5 to 7 seconds on account of the slipping of the feed- 

 rolls and overexposure of the paper. Notwithstanding this, the record 

 shows that the duration of the cycle had lengthened from the walking 

 duration of 0.4 second to approximately 0.6 second, and, further, that 

 the variations of a standing pulse had begun to appear, which have 

 already been noted in previous discussion of figure 40 and of curve A 

 in this figure. 



Curve E is similar to but not continuous with curve D, and repre- 

 sents the pulse measured with lengthened time-intervals after the 

 subject had been standing for 14 minutes. A wide variation in the 

 duration of cycles is seen in the curve, but this variation differs from 

 that in the other standing records, as here a pronounced rhythm is 

 present, occurring with each 12 to 14 cycles. At first thought it 

 might be said that this rhythm was connected with the respiration, 

 but assuming the average pulse-cycle duration in the curve is 0.73 

 second, the time-intervals for the rhythm would be nearly 10 seconds, 

 corresponding to a respiration-rate of 6 respirations per minute. 

 As seen in table 86 (p. 306), the average respiration-rate 24 minutes 

 after walking ceased on February 29 was 16.9, and it is unlikely that 

 it could have approached the rate required by the estimated length of 

 the rhythm. The record was made during the middle of the period, 

 when conditions were free from any disturbances which might have a 

 tendency to stimulate or retard the pulse-cycle. The cause of the 

 evident rhythm remains unexplained. 



The changes in the duration of the pulse-cycle after walking ceased 

 are also shown in the four curves in figure 42. These curves are con- 

 structed in the same way as those in figure 39, each point indicating 

 the average duration of a pulse-cycle as calculated from the measure- 

 ment of a group of 10 cycles, and each square in the figure representing 

 100 cycles. The ordinates, however, have been drawn to a larger scale 

 than in figure 39. The variations in the pulse-cycles thus appear larger 

 than in the curves in figure 39. 



In curve A the duration of the pulse-cycle for the subject walking is 

 between 0.33 and 0.34 second. During the first 50 cycles following 

 the transition, the duration lengthened to 0.36 second, with a total 



