The portion of the curves to the left of the heavy vertical line represents the pulse cycles during quiet. Between the heavy vertical line and the short lines through the curves is the period of exertion. The portion at the right of the short verticals is for the period of recuperation.

Different subjects show, naturally, individual peculiarities in their curves for changes in pulse-cycle length during and following the short periods of exertion but, in general, the pulse-cycle length required for the exercise tends with any individual to be a constant, no matter what the resting level may be.1

It is rather difficult to place the data for these pulse changes in quantitative terms for comparison. An effort in this direction is made in tables 94 and 95 for Squads A and B, respectively. The three figures given for any subject and date represent the average pulse-cycle length in 0.01 second in the three different portions of the record. For example, with Bro on October 28, 0.92" is the average pulse-cycle length of the 6 pulse cycles in the portion of the record which preceded the beginning of activity, 0.66" is the average for all of the pulse cycles which came within the limits of the activity, and 0.67" the average of the 20 pulse cycles which followed the cessation of activity. (See table 94.) With each subject these same conditions for the averages apply. All the members of Squad A, excluding Kon and Spe,2 show averages for October 28 of 103 for the period of quiet, 75 for the period of activity, and 79 for the first 20 pulse cycles in recuperation following activity. Assuming the duration of pulse cycles during "quiet" as a basis for calculation, we have for activity and rest 72.8 and 76.6 per cent, respectively, as shown in the extreme right-hand column of the table. Therefore the average cycle-length during the period of activity was 27.2 per cent shorter than during the quiet, and in the 20 beats following the activity it was still on the average 23.4 per cent shorter than during the period of quiet.3

The low diet average for Squad A for the 5 dates, October 28, November 11, December 9, January 13, and January 27, and for the 10 men whose records were averaged (Kon and Spe omitted) are 109, 77, and 85 for quiet, activity, and rest, respectively. The activity and rest are but 70.6 and 78.0 per cent of the quiet pulse-cycle length. The individual subjects show an average pulse-cycle length under conditions of quiet which ranges from 87 to 125 - Tom and Pea. Two other subjects, Vea and Pec, are very close to this upper value: that is, they each have 124 for pulse-cycle length corresponding with a rate per minute of 48 beats. The pulse-cycle length during activity shows a range from 65 to 95 for Tom and Vea, respectively. It is worthy of note that Vea, whose pulse has been spoken of in other connections (see p. 387) as so remarkably low, showed a cycle-length during activity considerably longer than that of Pec and Pea, whose quiet pulse length was at the same level with Vea. On the other hand, Pea and Pec show greater changes between activity and the subsequent rest than does Vea. The resting level ranges from 67 to 99 for Tom and Pea, respectively. In terms of per cent the activity is from 61.4 to 76.6 (Gar and Vea) of the quiet pulse-cycle length and the resting percentage is from 65.6 to 89.6 with Gar and Mon, the latter demonstrating unus-ally quick recovery in pulse-cycle length following the activity.

1 Miles, Carnegie Inst. Wash. Pub. No. 266, 1918, p. 102 ff.; see figs. 12, 13, and 14. This was found to be the case, also, when a subject was under the influence of small amounts of alcohol.

2 Kon came into Squad A late and Spe was ill alter December. These two subjects were omitted from the averages in the neuro-muscular measurements. See p. 657.

3 While a shorter pulse-cycle length means a faster rate per minute, the quantitative statement for change in the one can not be directly transferred to the other. The average cycle lengths, 103, 75, and 79, in terms of rate would equal 58, 80, and 76, respectively. The activity and rest sections therefore show increments of 22 and 18 beats per minute over the quiet, which was 58. These changes in terms of rate are 38 and 31 per cent as compared to the 27.2 and 23.4 per cent for changes in cycle length.

Table 94. - Different Levels Of Pulse-Cycle Length With Conditions Of Quiet, Activity, And Rest For The Men Of Squad A

[Values in 0.01 second for pulse-cycle length].

1 On account of the operation which Tom had in early January he was not asked to do the chinning on this date.