52 THE ROYAL SOCIETY OF CANADA 



Fig. 3. — Kymograph record of lever attached to ventricles of a 

 rabbit's heart, profused with Ringer's solution by the coronary system. 

 The bottom line marks time in seconds. The white spots on the heart 

 tracing were produced by sparks from the pointer, employed to signal 

 the moment of stimulation of the ventricle by induction shocks. The 

 first stimulus applied fell within the refractory phase, the second 

 stimulus, just outside the refractory phase, produced fibrillation. 

 Temperature 24-7°C. 



Fig. 4. — From same experiment as previous figure but one hour 

 later. Temperature 22-5 °C. Signals as before. Shows that stimuli 

 too early or too late are ineffective in producing fibrillation. The 

 last stimulus applied arrives at the critical instant. 



Fig. 5. — Electrograms taken with Einthoven galvanometer from 

 profused rabbit's heart. The abscissae represent fiftieths and tenths 

 of a second. Temperature 26°C. Electrodes for galvanometer on rt. 

 auricle and 1. ventricle. (1) shows spontaneous beats, (2), (3), (4) 

 shows stages of fibrillation induced by induction shock. The kymo- 

 graph tracing at the bottom serves as a key. The electrograms were 

 taken during the process of the kymograph record at the times indi- 

 cated by the longer lines projecting from the time tracing, which 

 represents seconds as before. 



