CARDIAC NERVES. 227 



pulsations. 1 This fact we have repeatedly verified in public 

 demonstrations. 3 Still another curious fact remains bearing 

 on the question under consideration. If powerful galvani- 

 zation, which immediately arrests the cardiac pulsations, be 

 continued for a certain time, so that the motor filaments 

 become temporarily exhausted and lose their irritability, the 

 heart resumes its contractions, notwithstanding that the 

 galvanization is continued ; the nerves being for the time 

 incapable of transmitting the inhibitory influence. 3 



The source of the motor filaments in the pneumogastrics 

 which exert a direct inhibitory action upon the heart be- 

 comes an important point to determine. In the original 

 experiments by the brothers Weber, it was shown that, when 

 the galvanic stimulus was applied to that portion of the 

 centres from which the nerves take their origin, the action 

 of the heart was arrested in the same way as when the nerves 

 themselves are galvanized ; 4 and it has been shown by sub- 

 sequent observations, that when the heart is thus s arrested 

 by galvanization of the medulla oblongata, if both pneumo- 

 gastrics be divided in the neck, its action is resumed. 5 This 

 would at first sight lead to the supposition that the inhibi- 

 tory filaments are derived from the roots themselves of the 



1 BERNARD, Lemons sur les effete des substances toxiques et medicamenteuses, 

 Paris, 1857, p. 348. 



2 In the inferior classes of animals, there are some exceptional phenomena 

 with regard to the pneumogastrics. In experiments made upon alligators, in 

 Xew Orleans, in 1861, we found that the action of the heart was promptly ar- 

 rested by galvanizing the nerves in the neck, when the animal was killed and 

 the general motor nerves were paralyzed by woorara. In some additional ex- 

 periments, we showed that all of the nerves were not affected by the poison after 

 the same length of time, and that the pneumogastrics were probably the last to 

 come under its influence. (See vol. i., Circulation, 1866, p. 234.) Bernard states, 

 also, that galvanization of the nerves in birds does not affect the heart, a fact 

 for which he offers no explanation. (BERNARD, Systeme nervevx, Paris, 1858, 

 tome ii., p. 394.) 



3 LONGET, Traite de physiologic, Paris, 1869, tome ii., p. 117. 



4 WEBER, in WAGNER, Handworterbuch der Physiologic, Braunschweig, 1846, 

 Bd. in., Zweite Abtheilung, S. 42. 



5 LONGET, Traite de phy&iologie, Paris, 1869, tome ii., p. 117. 



