466 BELL SYSTEM TECHNICAL JOURNAL 



degeneration in the brain. This is of fundamental importance in the 

 development of practical recovery methods. Wiggers recently has 

 pointed out that maintenance of coronary circulation is essential for 

 recovery from fibrillation. 



Were suitable arrangements and methods developed for the practical 

 application of counter-shocks, such shocks might be applied mistakenly 

 to a victim whose heart was not in ventricular fibrillation. To deter- 

 mine whether in such an event ventricular fibrillation would be caused, 

 5 "counter-shocks" of about 25 amperes for about 0.06 second were 

 applied to each of 9 sheep whose hearts were beating normally. Only 

 3 of the 45 shocks applied caused fibrillation, and in every such case 

 recovery was obtained by the immediate application of another 

 similar shock. This experiment was performed in 1932 prior to the 

 development of apparatus for the controlled placement of short shocks, 

 so that the shocks naturally fell at random. It was also prior to the 

 determination that such high-current shocks of short duration were not 

 likely to cause fibrillation even when the shock occurred during the 

 sensitive phase of the heart cycle. In the light of the subsequent 

 experiments, it is evident that the liability of causing ventricular 

 fibrillation by randomly placed short shocks at the high currents 

 employed in counter-shock is small. 



Summary of Results and Conclusions 



1. Current rather than voltage is the proper criterion of shock 

 intensity. 



2. The stimulating effect of current through the heart can derange 

 its action, causing ventricular fibrillation without damage to the 

 cardiac tissues but resulting in death within a few minutes, unless 

 the fibrillation is arrested. 



3. A current just below the threshold for ventricular fibrillation is 

 the maximum to which man safely may be subjected. Based upon 

 numerous tests on animals of several species comparable in size with 

 man, this maximum current is about 0.1 ampere at 60 cycles for a 

 duration of one second or more and a pathway between an arm and a 

 leg. 



4. The threshold fibrillating current is affected by: 



a. Species and Size of Animal. Among the dilTerent species the 

 threshold current increases roughly with both body weight and heart 

 weight. 



b. Current Pathway. Pathways from arm to leg, across the chest, 

 chest to arm, and head to leg may be expected to give about the same 

 threshold current. The pathway between the arms would be expected 



