494 



Drs. T. L. Brunton and T. Cash. 



The propagation of the wave in an upward direction, viz., from 

 ventricle to auricle, is not so regular as in the normal heart, the time 

 elapsing, when it does occur between the ventricular and auricular 

 systole, bearing a relationship to the degree of cold produced. Whilst 

 the ventricle is reduplicating in response to direct stimulation, the 

 auricle may maintain its regular rhythm. Stimulation of the venous 

 sinus almost invariably gives an auricular contraction at all times 

 preceding the ventricular. It has been already shown that in the 

 case of the normal heart stimulation in advanced diastole frequently 

 causes a spontaneous auricular and ventricular contraction, or a 

 ventricular beat preceding the auricular. 



In the heated heart we have noticed, in addition to the excessive 

 diminution or abolition of the refractory period in the ventricle 

 already observed by Marey, that usually the refractory period in the 

 auricle entirely disappears. A single stimulation of the ventricle 

 sometimes gives rise to a series of contractions with incomplete 

 relaxation intervening. After this has occurred, or after a simple 

 reduplication has been caused, it often happens that the auricular 

 beat occurring in normal sequence is not followed by ventricular, 

 which seems to show a temporary state of exhaustion of the ventricle. 

 In the heated heart the duration of a systole is so short that two beats 

 immediately succeeding one another may be perfectly distinct, while, 

 in the normal heart, the second one would have fallen within the 

 time of the systole of the first, so that it could only have appeared, if 

 it were possible at all, as an increase either of the height or length of 

 the first systole. Inhibition occurs in the heated heart as well as in 

 the normal, which is most frequently observed upon stimulation of 

 the venous sinus, and it is frequently at this time associated with a 

 reduplicated auricular contraction. The effect of strychnia is to pro- 

 long the refractory period of the ventricle. Stimulation of the ventricle 

 is frequently succeeded by contraction of the auricle. There is an 

 increased tendency for stimulation of the ventricle to induce a beat of 

 the auricle preceding the ventricular systole. There is less tendency 

 for the stimulation of the venous sinus or auricle to induce a beat of 

 the ventricle succeeded by one of the auricle ; and, indeed, this only 

 occurs when the stimulus falls just at the end of the ventricular 

 systole, i.e., when the ventricle itself is most sensitive. These facts 

 seem to indicate that the nervous channels are more active in trans- 

 mitting stimuli, both downwards from the venous sinus to the auricle 

 and ventricle, and from the ventricle back to the auricle. 



In its effect upon the refractory period, and in the tendency it 

 produces to maintain the regular rhythm, the action of strychnia 

 agrees with that of cold, as shown in the present series of experiments ; 

 but, as we have already shown in a former paper,* its effect in causing 



* " St. Bartholomew's Hosp. Reports," vol. xvi, p. 229. 



