DESCRIPTION OF APPARATUS. 37 



METHOD OF RECORDING THE RESPIRATION-RATE. 



The rise and fall of the rubber bag or tension equalizer with each 

 expiration and inspiration can be readily counted by an observer, 

 thus giving an admirable index of the respiration. As a matter of 

 fact, during the conduct of a severe-work experiment of this type, the 

 other observations are so numerous that it is at best very difficult for 

 an observer to concentrate his attention upon such counting. A 

 tambour has therefore been connected to the petcock S (see fig. 2) 

 which is moved by the difference in pressure existing in the connection 

 between the mouthpiece and the tension equalizer. With each exhala- 

 tion a slight pressure is exerted upon the tambour which records upon 

 a kymograph drum. Subsequently an accurate count of the number of 

 respirations per minute and for the entire experimental period may be 

 made from the tambour record and that of a time marker. 



METHOD OF RECORDING THE PULSE-RATE. 



The important relationship between total metabolism and the pulse- 

 rate, which has been so frequently observed in this Laboratory, made it 

 desirable to secure records of the pulse-rate of the subject during the 

 walking periods. The difficulties experienced in securing counts of the 

 pulse-rate in the earlier research with the bicycle rider have been freely 

 commented upon in the publication giving the report of that study, and 

 it was hoped that some graphic method could be found which would give 

 accurate records of the pulse-rate of a walking man. Unfortunately 

 such a method was not available at the beginning of our research, and 

 counts were therefore made at the wrist or with a stethoscope. Even 

 with a stethoscope at some distance, as employed by Krogh, 1 the noise 

 of the treadmill was such as to make the counting of the pulse-rate 

 extremely difficult. Various forms of tambours 2 were also experimented 

 with in an attempt to register the pulse graphically, but without result. 

 Finally, by using body leads and the Bock-Thoma oscillograph or the 

 Einthoven string galvanometer, we were able to secure graphic records 

 of the pulse-rate of the subject while he was walking upon the treadmill. 



Great difficulty was experienced in such photographic registration 

 with the delicate oscillograph and string galvanometer, for not only 

 were there leakages of the 220- volt current used for the motor, but also 

 a static charge on the rapidly revolving belt. Various devices were 

 used for obviating these difficulties, such as having the subject wear 

 rubber-soled shoes and even rubbers over the shoes, but with little 

 success. Finally a metallic brush was made of a piece of brass tubing, 

 69 cm. long, to which pieces of brass chain, 7 to 9 cm. long, were 

 attached at intervals of approximately 1.5 cm. This brush was so 

 attached to the treadmill that the ends of the chains lay upon the 



, Skand. Archiv f. Physiol., 1913, 30, p. 375. 

 2 Bowen, Contributions to Medical Research dedicated to Victor Clarence Vaughan, June 1903, 

 p. 462, Ann Arbor, Mich. 



