PHYSIOLOGICAL CHANGES IN TRANSITION. 297 



4 to 5 times within the first minute and the increase was practically 

 over within 3 minutes. Under reverse conditions, i. e., in the transi- 

 tion from walking to standing, the respiration-rate fell slowly and 

 irregularly and was not settled nor at its normal value within 8 minutes. 

 The ventilation-rate fell promptly and within 1 minute was one-half of 

 the value found with the subject walking, this decrease continuing, but 

 with diminishing force; after 8 minutes of standing it was still above 

 the normal. The oxygen consumption was in harmony with the pul- 

 monary ventilation, falling continuously but not reaching a pre- 

 walking normal value during the 6 minutes of measurement. 



PULSE-RATE IN TRANSITION PROM STANDING TO GRADE WALKING. 



In the comparison of the pulse-rate for the standing position with 

 that in grade walking (see p. 262), it was seen that the rate in the walk- 

 ing periods increased largely, the size of the increases depending upon 

 the amount of work done. The results are given graphically in figures 

 30 to 32, inclusive, pages 265 to 267. The duration of the preliminary 

 walking before the experimental period began varied somewhat, but 

 was rarely, if ever, less than 5 minutes, and in most cases more nearly 

 15 minutes. During this preliminary walking it was assumed that the 

 metabolism and physiological factors had become adjusted to the new 

 demand and that the body functions were acting on a constant, though 

 higher, plane. This assumption was confirmed by the general picture 

 for the respiration, ventilation, and oxygen consumption previously 

 discussed. (See pp. 278 to 287.) The new level in these cases was 

 reached by or before the fourth minute of exercise, and most of the 

 change occurred inside of 1 minute after the exercise began. 



To obtain some estimate of the alterations which take place in the 

 pulse-rate during the time of change from quiescence to grade walking, 

 a number of electro-cardiograms were made for E. D. B. in the period 

 extending from one-half minute before the grade walking began through 

 the first or second minute of exercise. In addition, some records were 

 made in the change from walking to standing at the end of the experi- 

 mental period. 



These changing pulse-rates have been termed the transition pulse- 

 rates. To express the rapid alteration in the heart-action under 

 these conditions, we have used the duration of the pulse-cycle. While 

 the most desirable method of recording these changes would naturally 

 be to have the time-intervals on the photographic paper of such size 

 that each pulse-cycle could be readily measured in 0.01 second, the 

 labor and the time involved precluded any extended use of this method. 

 It should be remembered that in all this work our interest was in the 

 pulse-rate and, as explained on page 34, the electro-cardiogram was 

 used simply as a means of determining that factor and not to study 

 the type or peculiarities of the pulse-cycle. On two occasions (Feb- 

 ruary 28 and 29) the paper was run through the camera with such 

 rapidity that it was possible to measure the durations of the individual 

 cycles. Ordinarily, however, the rate of movement was so adjusted 



