176 



Scientific Proceedings (120). 



Records at suitable times and for different purposes were then 

 obtainable of the usual lead 2, and of excitation at the base and 

 at the apex of the auricle. A combination of any two records 

 could be taken. Electrodes for sending break shocks into the 

 auricles were permanently fixed in the auricle near the sulcus 

 terminalis. The vagi remained undisturbed. The rate of the 

 heart was natural. By taking simultaneous records of the excita- 

 tion at the base and apex of the auricle, the distance between the 

 electrodes being known, the rate of conduction could be calculated. 

 The refractory period could be known exactly by obtaining and 

 arranging in series the duration of the periods after the waves of 

 auricular activity which the break shock terminated (Table I). 

 These periods fall into two groups: those in which the break 

 shocks fail to elicit a response, and those which bring about a 

 response. The longest of the periods after which a shock fails to 

 elicit a response is the refractory period. The break shocks were 

 signalled by a special device to the camera and were photographed. 

 They were likewise signalled and inscribed on the smoked record 

 of the blood pressure. Records were made before and after 

 injecting quinidine. 



We report now on six experiments (Table II). The refractory 

 period rose in four: 0.0042 sec. (Exp. 39), .0502 sec. (Exp. 47), 

 0.0336 sec. (Exp. 48), 0.0120 sec. (Exp. 46), and fell in two: 0.0101 

 sec. (Exp. 41) and 0.0084 sec. (Exp. 42). In two the change, 

 one upward and one downward, was insignificant (Exps. 39 and 

 42). The rate of conduction fell in four (Exps. 39, 42, 46 and 47), 

 and remained practically unchanged in one (Exp. 48). In experi- 

 ment 41, the change in this rate is unknown. It is important to 

 point out that after injecting quinidine the heart rate rose 4 times 

 (Exps. 39, 46, 47 and 48). In experiment 46, the rate fell after 

 subsequent injections. In two experiments (Exps. 41 and 42) the 

 rate fell though the change was slight. In the cases in which the 

 rate rose there was an increase in the duration of the refractory 

 period. This result is contrary to what is anticipated, for with 

 a rise in rate, Lewis's experiments lead one to expect a fall in this 

 measurement. In cases in which the rate fell, there was a fall 

 also in the length of the refractory period. 



If the circus movement, as it is now believed, underlies the 

 state of fibrillation, and if it depends on the factors which have 



