154 VITALITY AND EFFICIENCY WITH RESTRICTED DIET. 



the edge of the metal strip and all were secured to the felt at the back. 

 A regular 4-foot telephone cable, with wires designated, which ends in 

 the usual switchboard plug fitting into the ordinary receptacle was 

 employed for purposes of connection. This offers very quick con- 

 nection and good contact. The gauze on the face of the pad was 

 moistened in warm saturated sodium chloride solution. Pads R and 

 L were placed in contact with the skin on the right and left sides of 

 the subject; G was placed between them and somewhat lower on the 

 abdomen. Two bands of elastic tape about the subject's chest held 

 the pads in position. This tape did not have to be uncomfortably 

 tight. Although unnecessary in these 

 experiments, the pads could be worn a 

 long time without annoyance, and they 

 made good contact with the body for an 

 indefinite time. The many thicknesses 

 of cotton gauze provided against any 

 scratching of the skin. R and L con- 

 nected with the two terminals of the gal- 

 vanometer string. G was connected to 

 earth as a "ground." This method was 

 found to be more satisfactory than to 

 earth the frame and coils of the string 

 galvanometer. With these electrodes it 

 was nearly always possible to get satis- 

 factory pulse records while the subject 

 was engaged in the vigorous activity 

 called for by the test.^ These same elec- 

 trodes were used in recording the pulse 

 when the subject walked on the treadmill 

 (seep. 129). Several sets of electrodes 

 facilitated the experimenting.- 



The electrocardiographic apparatus 

 had been arranged in general to facilitate the taking of such records. 

 In the nature of the case, it is most convenient to have the subject 

 near the apparatus, but the apparatus should not be such as to annoy 

 or distract the man. The electric motor which operated the camera 

 was placed in an adjoining room and could run indefinitely with no 

 disturbance. The illumination was from an automatic arc lamp. The 



* A prominent exception to this statement is found in Gul of Squad A. It could never be 

 determined with assurance whether the action currents from muscles of limbs and trunks were in 

 his case exceedingly strong or whether this subject carried about in his body an immense static 

 charge. However, almost every time he was tested he put the galvanometer string out of order. 

 His case was exceptional. Nothing similar was encountered in a group of 65 young men tested 

 previous to this research. No criticism is made of him, for he followed instructions as well as 

 any subject could. 



^ These electrodes might not be the most satisfactory form for long periods of walking or other 

 physical exertion, as they could shift into position of contact, one with the other, unless special 

 arrangement was made to avoid this. 



Fig. 26. — The body electrodes 

 used in recording electrocardio- 

 grams during physical activity. 



The pads were 1 1 cm. wide and 20 cm. 

 long; each pad was made of 8 lay- 

 ers of cloth, a sheet of thin metal, 

 and a piece of felt for backing. In 

 use, the cloth is moistened in salt 

 solution. R and L were applied 

 directly to the skin on the right 

 and left sides of the subject and 

 connected to the string galvanom- 

 eter. G was applied just above 

 the navel and connected to ground ; 

 P, regular 3-lead telephone plug. 



