CAUSES OF ARREST OF THE ACTION OF THE HEART. 239 



produced instantaneous death. On post-mortem examination 

 no lesion was discovered. Though these cases are rare, they 

 are well known, and the effects are generally attributed to 

 injury of the solar plexus. The distress is precisely what 

 would occur from sudden arrest of the heart's action ; for it 

 is the blood charged with oxygen and sent by the heart to 

 the system, which supplies the wants of the tissues, and not 

 the simple entrance of air into the lungs ; and arrest of the 

 circulation of arterial blood, from any cause, produces suffo- 

 cation as completely as though the trachea were ligated. 

 This fact is clearly proven by experiments in the article re- 

 ferred to above. It is a question whether the arrest of the 

 heart, if this be the pathological condition, be due to concus- 

 sion of the nervous centre, or to the direct effects of the blow 

 upon the organ itself. Our present data do not enable us to 

 answer this question definitely, but rather incline us to the 

 opinion that in such accidents the symptoms are due to direct 

 injury of the heart. An additional argument in favor of this 

 view is founded on our knowledge of the mode of operation 

 of the sympathetic system. The effects of stimulation or 

 irritation of this system are not instantaneously manifested, 

 as is the case in the cerebro-spinal system, but are developed 

 slowly and gradually. 



As far as we have been able to learn by experiment, the 

 nervous influences which arrest the action of the heart oper- 

 ate through the pneumogastrics. As we have just seen, we 

 can closely imitate this action by galvanism. The causes of 

 arrest in this way are numerous. Among them may be men- 

 tioned, sudden and severe bodily pain and severe mental 

 emotions. With the exceptions of arrest of the heart from 

 loss of blood and from distention, from whatever cause it may 

 occur, stoppage of the heart takes place through the nervous 

 system. It may be temporary, as in syncope, or it may be 

 permanent; examples of which, though rare, are sufficiently 

 well authenticated. 



