PHYSIOLOGICAL EFFECTS 159 
was performing effective muscular work corresponding to approximately 1 
calorie per minute, or a total energy output of about 6 calories per minute. 
It is greatly to be regretted that temperature observations could not have 
been made at the time the amount of the external muscular work was 
double that when these records were made. 
The observations for the experiment of December 21 include only the 
records for the body-temperature immediately following the cessation of work. 
The record obtained shortly after the work ended, i. e., 37.84° C. at 10 h 45 m 
a.m., is the highest record secured for any of the experiments. The rapid 
persistent fall in temperature amounted to nearly 1.6° C. inside of an hour. 
As will be seen by the curve, the body-temperature was assuming a constant 
level when the observations were discontinued. 
The most complete- series of records obtained in the three experiments 
was that for December 22, which included observations before, during, and 
after work, the thermometer being kept in the rectum throughout the whole 
period of work. In the rest-periods when the subject lay upon the couch, 
the temperature in the rectum was reasonably constant at 36.25° C. The 
work began at 9 h 28 m a.m., and in 7 minutes the temperature had risen 
rapidly, this rise continuing at almost the same rate until 9 h 55 m a.m., 
or 27 minutes after the work began, when the thermometer registered 37.66° C, 
representing an increase in the body-temperature of 1.4° C. This very high 
temperature was not maintained, however, for as the work progressed, there 
was a slight falling off, with a tendency to assume a level at 37.36° C. The 
subject stopped working at 10 h 50 m a.m., and the characteristic rapid fall in 
temperature after work is again shown in this curve, the temperature ulti- 
mately reaching approximately the level shown for the observations prior to 
the work. 
The laboratory protocols for the experiment of December 22 have a 
special interest in this connection. They show that when the subject began 
working at 9 h 28 m a.m., he worked very hard and as rapidly as possible 
until 9 h 53 m a.m. Unfortunately no record of the number of revolutions was 
obtained as the registering counter broke shortly after the work was begun. 
At 9 h 53 m a.m. the subject without stopping adjusted the rate of riding to 
60 revolutions per minute. Singularly enough, this experiment is one in 
which the impending collapse appeared, so that at 10 h 10 m a.m. it was neces- 
sary for him to remove his mouth from the mouthpiece of the respiration 
apparatus. After an intermission of about 3 minutes, he resumed work, the 
rate throughout the rest of the experiment being essentially 58 to 60 revolu- 
tions per minute. It is thus seen that the rapid work at the beginning raised 
the body-temperature to the highest point, and that the falling off shown 
by the curve later was actually coincident with a considerable diminution 
in the amount of work done. 
It will be noted that all of these values were taken deep in the rectum 
with a very sensitive thermometer, giving accurate measurements to 0.01° C. 
The difficulties incidental to measuring the body-temperature of athletes 
during severe exercise have often been pointed out, and bicycle riding appears 
to offer the most ideal conditions for studying the influence of muscular 
activity on body-temperature. From the results obtained with two subjects 
in earlier observations, we have no reason to believe that a study of body- 
