rate even during severe muscular work, very closely followed the amount of the energy output, an observation that is fully in accord with the values secured with normal resting subjects which show that the pulse-rate and the total metabolism are intimately related. Although innumerable observations of the pulse-rate were made in this study, it seems unnecessary to report these in detail, and we accordingly give only a few series of pulse-rate observations which were made before, during, and after the work with each of the intensities of muscular work performed. The values for 4 experiments in which the subject was producing approximately 1.05 calories of external muscular work per minute are indicated by the curves in fig. 6. Before the experiments, when the subject was lying quietly, the pulse-rate was usually not far from 60 to 64 per minute, but after the work began there was a rapid ascent of the pulse-rate until it reached an average not far from 125 per minute with this degree of muscular activity. Immediately on the cessation of work, which is indicated on the chart by arrows, the pulse began to fall, the first observation being invariably many beats per minute less, although there was a distinct tendency for the pulserate after the work to become stationary at a higher level than it was before. With an external work production of 1.5 calories per minute, the changes in the pulse-rate were even more strikingly marked, as shown by fig. 7. Here again with an average rate during rest of approximately 64, there was inside of 20 minutes a rise in the pulse-rate to a level of approximately 160 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 FIG. 7.-Curves showing the pulse-rate when the external muscular work was equivalent to 1.5 calories per minute. per minute. With the cessation of work, the pulse fell rapidly, and the first values obtained in the rest-period after work were invariably much lower. The tendency for the pulse-rate to stop at a much higher level than before the experiment is even more clearly shown than in fig. 6, the average level after work for these 4 experiments being not far from 83 beats per minute, as com pared with an initial value before work of 64 per minute. With this intensity of work, therefore, which was nearly 50 per cent greater per minute than that in the experiments shown in fig. 6, there was an average rise in the pulse-rate from 64 to 160 or approximately 35 beats per minute higher than when the muscular work was 1.05 calories per minute. The curves for the pulse-rate in 5 experiments in which the external muscular work was 2.0 calories per minute are given in fig. 8. These values show an average pulse-rate before work of about 60 per minute with an almost immediate rise inside of 15 or 20 minutes to a level of approximately 163, 180 170 160 150 140 130 120 110 100 90 80 70 60 50 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 FIG. 8.-Curves showing the pulse-rate when the external muscular work was equivalent to 2.0 calories per minute. which continued throughout the work. After work the pulse-rate fell rapidly but became constant at a distinctly higher level than that before the work began. The average maximum rate, i. e., 163 per minute, is but a little higher than that with 1.5 calories of work. The average values for the pulse-rate in two experiments in which the external muscular work was 2.25 calories per minute are plotted in fig. 9. The initial pulse-rate before work averaged as usual about 63, rising rapidly at the beginning of work, and seeking a level not far from 166, or essentially that with the work at 2 calories per minute. After the work ceased, there was again a rapid fall with a striking tendency for the pulse to remain above the initial level. In view of the single high observation of 180 per minute, it is to be regretted that more observations could not have been obtained during this severe muscular work. As has already been pointed out, some method other than the radial pulse or the stethoscope must be used during muscular work in order to obtain satisfactory records of the pulse-rate, but these two methods were the only ones available at the time, since we did not wish to hamper the subject with a chest pneumograph and a string galvanometer was not then at our disposal. It is evident, however, that there is here an interesting field for study in the relation between the pulse-rate and the intensity of muscular work. One of the points clearly brought out in this study of the effect of muscular work on the pulse-rate is the distinct tendency for the pulse to settle 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 FIG. 9.-Curves showing the pulse-rate when the external muscular work was equivalent to 2.25 calories per minute. a to a much higher level than prior to work. In connection with fig. 8, it should be noted that the pulse-rate continued on a level higher than the initial values so long as the observations were made, a record of 76 being obtained 361 minutes after the beginning of the work. Following one of the experiments shown on fig. 9, the high pulse-rate of 70 or over continued up to the 400th minute when the observations were discontinued. This is in complete correlation with the higher metabolism found under these conditions which is discussed elsewhere in this report. Our results are strikingly at variance with the observations of Cook and Pembrey," who maintain that with welltrained persons the pulse-rate after a strenuous run rapidly returned not only to the earlier level but actually fell below. Only with poorly trained individuals did the pulse remain high after exercise. Our subject M. A. M. was admirably trained and usually very fit, as the amounts of work done without food amply testify. Inasmuch as in our experiments the pulse-rate showed an even greater tendency towards this persistency in maintaining a higher level after work than did the metabolism, a series of experiments definitely planned to study this interesting point should be made; in this research, a See p. 163. b Cook and Pembrey, Journ. Physiol., 1912, 45, Proceedings, p. 1. the pulse-rate observations after work, as well as the body-temperature measurements, were wholly incidental to the major questions being studied, and both the nature of the experiments and the temperament of the subject made it impossible for us to hold him in the laboratory an undue length of time even for securing pulse-rate observations of such interest and value. While there is a general tendency for the high level of the pulse-rate during severe muscular work to increase as the intensity of the work increases, the values being respectively 125 beats per minute for external muscular work of 1.05 calories, 160 per minute for 1.5 calories, 163 per minute for 2 calories, and 166 for 2.25 calories, the relationship is not so simple as would appear, for in the experiment of March 15, in which the work of about 2 calories per minute was so prolonged and continuous as to produce a condition of fatigue, the observations during the six experimental periods were as follows: At the 34th minute, 128 beats; 40th minute, 130; 78th minute, 128; 125th minute, 136; 174th minute, 156; and 211th minute, 160. While general deductions are not warranted from this single series of observations during prolonged work, yet it is of interest to note that the work in the last three periods became more and more difficult, and in the last period it was necessary to stop work at the end of 7 minutes instead of the usual 10 minutes. The rise in the pulse-rate noted in the previous section as accompanying the condition of collapse is not here discussed since it would be obviously improper to consider in this connection values obtained under such abnormal conditions. BODY-TEMPERATURE. With the special equipment installed in this laboratory " for the accurate measurement of the rectal body-temperature, it was hoped that during this research it would be possible to obtain many records of the body-temperature during severe muscular work. As a matter of fact, observations could be obtained only on three days, December 20, 21, and 22, 1911, with subject M. A. M. At the end of this time the subject complained that the thermometer irritated him and rather than jeopardize the whole series of experiments by insisting upon the rectal temperature measurements, they were discontinued. In but few instances have such measurements been obtained during the actual progress of muscular work, the most extensive series with which we are familiar being that of Benedict and Snell. In this series, two experiments are reported in which the subject, J. C. W., rode a bicycle ergometer. The results, which are presented in the form of curves, show that there was an immediate rise on beginning work until a maximum temperature was reached which remained essentially constant throughout the working period. After the work was discontinued, the temperature rapidly fell. The thermometer with which the observations of Benedict and Snell were made was much larger than that employed in this research as in the earlier observations the resistance thermometer principle was used, while with the newer apparatus the records were made by means of the thermal junction only. In our thermal-junction thermometer the connections are covered for some 25 centimeters by a small flexible rubber tube, approximately 3.5 a Benedict and Slack, Carnegie Institution of Washington Publication No. 155, 1911. millimeters in diameter. When the subject is at rest, the thermometer is tolerated for hours at a time without the slightest inconvenience; in fact after the thermometer has been inserted for 5 minutes, the subject is usually unconscious of its presence. On the other hand, when the subject is riding at high speed on the bicycle ergometer, more strain is naturally brought upon the sphincter, which increases the possibility of irritation, so that the objection of the subject to the thermometer could be easily understood. The few observations made were, however, very accurate and representing as they do records obtained during the actual time of severe muscular work, they have a somewhat unusual interest. The results have been plotted in the form of curves shown in fig. 10. In the first experiment of which the curve is shown, that of December 20, the work began about 9h 30m a.m., the initial record being made at 9h 35m a.m. Unfortunately no records were taken before the work began. In 20 minutes the temperature steadily rose from 36.39° C. to 37.08° C., then gradually mounted until at 10h 17m a.m. the temperature had reached 37.22° C. For a period of approximately 20 minutes, the measurements were lost and when resumed, the first observa AM.8.20 8.30 8.40 8.50 9.00 9.10 9.20 9.30 9.40 9.50 10.00 10.10 10.20 10.30 10.40 10.50 11.00 11.10 11.20 11.30 11.40 11.50 12.00 FIG. 10.-Continuous records of the rectal temperature obtained by thermal element during severe muscular work. The work began about 9h 30m a.m. and ended as indicated by the group of arrows on the chart. tion, which was taken just before the work ceased, gave a record of 37.39° C. After the work there was an immediate rapid fall which persisted until the observations were discontinued at 11h 40m a.m., at which time the bodytemperature was still falling. Throughout these observations, the subject |