PAROXYSMAL IRREGULARITY OF THE HEART II 



the heart. This impulse-emitting area was obviously in a state of great 

 irritability, for the impulses amounted to 150 per minute, and at the 

 same time the rhythm was extremely irregular. 



The sudden onset of irregularity and its temporary character suggest 

 that while there may be cardiac conditions favouring irregularity, the 

 actual change from the regular beat must be due to affection of other 

 organs. And the fact that it accompanied the nausea and vomiting, and 

 tended to recur when no exertion had been made, and especially in the 

 night time, suggest that the immediate cause of the irregularity was 

 some abnormality of the central nervous system acting on a damaged 

 heart. We are aware that the tendency at present is to regard such 

 conditions as of peripheral origin, and to exempt the central nervous 

 system from responsibility in such phenomena. At the same time, the 

 history of the case inevitably suggests this view, and we hope in the 

 following pages to show indisputably that the central nervous system is 

 capable of giving rise to very marked abnormalities of the heart action. 



Animal Experiments. 



In the course of the long series of experiments and demonstrations 

 on the dog's heart carried out in the pharmacological laboratory of the 

 University of Michigan, during the last ten years, it has happened 

 occasionally that on opening the chest the heart was found to be beating 

 very rapidly and irregularly. Doubtless other workers in this field may 

 have had similar unfortunate experiences, but we are unaware of any 

 recorded cases. Our dogs were anaesthetised with morphine 0'2-0'3 G. 

 hypodermically, and chloretone administered by the stomach tube. The 

 operation consisted in performing tracheotomy, prolonging the median 

 incision to the lower end of the sternum, sawing through the sternum 

 along its whole length and hooking the two sides of the chest apart, thus 

 exposing the pericardium, which was opened. The myocardiograph 

 was then applied to the ventricle and auricle, and tracings taken on a 

 kymograph with smoked paper. The anaesthesia was invariably deep 

 enough to prevent any manifestation of pain, and the eyelid reflex was 

 absent before the incision was made. Sometimes, however, spontaneous 

 respiratory movements returned while the sternum was being cut through, 

 or, if these were present before, they became quickened and deepened. 



(105) 



