METHODS OF MEASUREMENT. 37 



then passed between the legs and out through the fly of the walking 

 suit worn by the subject. The pointer on the dial of the Wheatstone 

 bridge was placed upon the 100 division-mark of the slide- wire and a 

 balance obtained with the compensating leads by an adjustable resist- 

 ance inserted between the galvanometer and the bridge. The com- 

 pensating leads were then replaced by the leads in the circuit of the 

 thermometer. At first the temperature records were secured at the 

 beginning and end of the periods, but after a few days they were taken 

 oftener, usually every 2 minutes, and sometimes every minute. Read- 

 ings were also made in the intervals between the periods. 



Balances with the compensating leads were made at intervals during 

 the forenoon. Between the periods, especially when the subject had 

 been walking, he was allowed to sit on a stool placed on the treadmill or 

 to stand erect. In either case it became necessary for his comfort to 

 throw a blanket around him. It was found that if the blanket in- 

 closed a portion of the leads (ordinary lamp cord), the balancing became 

 extremely difficult; consequently, care was exercised to prevent more 

 than 12 to 18 inches of the leads from being inclosed within the folds of 

 the blanket. It was also observed at times that sitting affected the 

 temperature reading, this being due, possibly, to a change in position of 

 the thermometer within the walls of the rectum. These conditions 

 were hard to avoid, but at all times the greatest care possible was used 

 in inserting the thermometer to a uniform depth and in balancing with 

 the compensating leads at frequent intervals. 



On a few days, when W. K. was doing a large amount of work, the 

 weather was warm and an electric fan was allowed to blow a current of 

 air across his face and shoulders. Except in these few experiments, the 

 subjects walked in the still air of the room, wearing heavier or lighter 

 clothing in proportion to the amount of work which they were expected 

 to perform. The effect of a moving air-current on the metabolism, 

 general comfort, and efficiency of an individual has been emphasized by 

 Hill in a recent report. 1 With the few exceptions stated above, we made 

 no attempt to control the body-temperature of the subject, other than 

 by keeping the room- temperature at approximately 20 C. and allowing 

 the use of a blanket after the cessation of the exercise of walking. 



DETERMINATION OF THE BLOOD-PRESSURE. 



During the last month of the study, that is, subsequent to March 19, 

 1916, some determinations were made of the blood-pressure of E. D. B. 

 as a part of the walking experiments. Attempts to record the blood- 

 pressure while the subject was walking were unsuccessful, on account of 

 the movements of the body. It was necessary, therefore, to make the 

 measurements immediately after the walking had ceased. The 



1 Hill, The science of ventilation and open air treatment, part I, Special Report, Ser. No. 32, 

 Medical Research Committee, London, 1919. 



