BEATS PER MINUTE 



Fig. 6. — Constancy of duration of relative refractory period and change in absolute refrac- 

 tory period as dog ventricular rate is increased. Ventricle driven directly ( ), auricular 



drive of ventricle (. .)• 



MA, 

 12.0 



X. 10.0 



-I 



I- 8.0 



. I 

 «/) UJ 



< tr 



6.0 



1.0 



0.5 



VENTRICULAR FIBRILLATION 



ADR.-3.IC.C. 



N0R.ADR.-2.7C.C. 



XXX 



\. 



V'' \ 



X X 



y XX 



X XX 



XXX 



XX 



Fig. 7. — Changes in diastolic threshold and fibrillation threshtilds of the dog ventricle fdllowinj: 

 injections of adrenalin and nor-adrcnalin (1:25,000). 



