236 CIRCULATION. 



For we know that when a set of muscles on one side is par- 

 alyzed, as in facial palsy, their tonicity is lost, they become 

 flaccid, and the muscles on the other side, without any effort 

 of the will, distort the features. 



"We can imitate an exaggeration of this force by a feeble 

 current of galvanism, which makes the pulsations of the heart 

 less frequent and more powerful ; or exaggerate it still more 

 by a more powerful current, which arrests the action of the 

 heart altogether. 



Phenomena are not wanting in the human subject which 

 verify these views. Causes which operate through the 

 nervous system frequently produce palpitation and irregular 

 action of the heart. Cases are not uncommon in which pal- 

 pitation habitually occurs after a full meal. There are in- 

 stances on record of immediate death from arrest of the 

 heart's action from fright, anger, grief, or other severe men- 

 tal emotions. Syncope from these causes is by no means un- 

 common. In the latter instance, when the heart resumes its 

 functions, the nervous shock carried along the pneumogastrics 

 is only sufficient to arrest its action temporarily. When 

 death takes place, the shock is so great that the heart never 

 recovers from its effects. 1 



Summary of certain Causes of Arrest of the Action of the 



Heart. 



In warm-blooded animals, the heart's action speedily 

 ceases after it is deprived of its natural stimulus, the blood. 

 It is not from experiments on the inferior animals alone that 

 we derive proof of this fact. It is well known that in profuse 

 hemorrhage in the human subject, the contractions of the 



91 An explanation of the influence of the pneumogastric nerves on the heart, 

 very like the one we have given, is made by Longet ( Traite de Physiologic, 

 Paris, 1861, tome i., p. 785); but this author assumes that the pneumogastrics 

 and the sympathetic have an antagonistic action, the former moderating, and the 

 latter accelerating the heart's action. 



