PHYSIOLOGICAL EFFECTS 157 
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 dur- 
ing 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 fol- 
lows: 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 ther- 
mometer irritated him and rather than jeopardize the whole series of experi- 
ments 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. 6 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 ear- 
lier 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. 
6 Benedict and Snell, Pflugers Archiv f. d. ges. Physiol., 1902, 90, p. 33. 
