,^o8 ON THE ACTION OF STRYCHNIA ON THE HEART. 



distributed in the ventricle and auricle, the greater number 

 being in the venous sinus and ventricle, and the fewest in the 

 auricle. 



When the sinus, then, is separated from the remainder of the 

 heart, the motor power in the auricles and ventricle is insufficient 

 to make them pulsate, although the ventricular ganglia are 

 sufficient, when separated from the auricle, to set the ventricle 

 in motion. This explanation is opposed to the fact that if the 

 venous sinus be gradually, instead of suddenly, separated from 

 the auricle, they will still continue to pulsate. Notwithstanding 

 this objection, however, it seems to us that this explanation, 

 although very probably it does not represent the whole truth, is 

 to a considerable extent true, and the cessation of the auricular 

 and ventricular movements, after the removal of the venous 

 sinus, is really due, in a great measure at least, to want of motor 

 power. It occurred to us that if this were so, we ought to be 

 able, by stimulation of the motor ganglia, to reinduce the cardiac 

 pulsations after they had ceased from ligature of the venous 

 sinus. It is well known that if a single galvanic shock be 

 applied to the ventricle when in this state of diastolic quiescence, 

 the ventricle will contract once at each application of the stimu- 

 lus, but the single pulsation is not succeeded by a succession of 

 rhythmical beats. As warmth has a very powerful effect in 

 increasing the cardiac activity, it seemed probable that the 

 application of warmth to the heart, when in the condition of 

 still-stand thus described, might so far stimulate its motor 

 ganglia as to allow it to resume its rhythmical pulsations. We 

 therefore induced complete still-stand in the frog's heart by 

 applying the ligature in the usual way. On then warming the 

 heart, either by directing upon it a current, of air heated by 

 passing it through a hot glass tube, or by bringing into its 

 neighbourhood a heated copper wire, we found that the rhyth- 

 mical pulsations again commenced, and continued for two or 

 three minutes after the time that warmth was applied. 



The cessation of the movements of the heart, after the 

 removal of the venous sinus, seemed to us analogous to the 

 cessation of respiratory movements and of vaso-motor tone after 

 the influence of the medulla oblongata has been removed by 



