460 



BELL SYSTEM TECHNICAL JOURNAL 



These results serve to indicate the probable threshold current for 

 man under similar conditions. The average weight of an adult man 

 is approximately 70 kilograms (154 lbs.) and his heart weight, 330 

 grams (.75 lbs.). The average threshold current for a body weight of 

 70 kilograms is 0.26 ampere and that corresponding to a heart weight of 

 330 grams is 0.29 ampere. Knowledge of such average currents is use- 

 ful, but in the practical application of this information it is the lower 

 limit of current causing ventricular fibrillation that must be taken into 

 consideration. The thresholds differ widely for different individuals of 

 the same species. The results on the whole indicate for man that cur- 

 rents in excess of 0.1 ampere at 60 cycles from hand to foot would be 

 dangerous for shock durations of three seconds or more. 



Effect of Frequency 

 To determine the effect of changing the frequency other tests were 

 made on sheep with 25-cycle current and direct current, the general 



UJ< 



0.2 0.3 0.5 0.7 1.0 2.0 



FIBRILLATING CURRENT- AMPERES 



3.0 



MINIMUM CURRENT CAUSING 



VENTRICULAR FIBRILLATION. 



MAXIMUM CURRENT NOT 



CAUSING VENTRICULAR 

 FIBRILLATION. 



25 

 FREQUENCY 



50 

 CYCLES PER SECOND 



Fig. 3 — Effect of freciuencv on threshold current causing ventricular fibrillation in 

 sheep. Shock duration 3 seconds. Electrodes on right fore and left hind legs. 



