CARDIAC NEKVES. 225 



one of the most interesting points in the physiology of the 

 circulation ; tut we can discuss the mechanism of the phe- 

 nomena following section of the nerves more satisfactorily 

 after we have considered the effects of their galvanization. 



Effects of Galvanizing the Pneumogastrics or tJielr 

 Branches upon the Circulation. The experiments upon the 

 effects of galvanization of the pneumogastrics in the neck 

 on the action of the heart are almost innumerable ; and, al- 

 though the explanations of the phenomena observed present 

 the widest differences, the facts themselves are sufficiently 

 simple. These facts will be discussed under the following 

 heads : 1. The direct influence of galvanization of the nerves 

 in the neck, undivided, or of galvanization of the peripheral 

 extremities of the trunks after division. 2. Reflex phenom- 

 ena following galvanization of the central ends of branches 

 of the pneumogastrics, after their division. 



Direct Influence of the Pneumogastrics on the Heart. 

 In 1846, the brothers Weber noted the important fact that 

 galvanization of the pneumogastrics in the neck rendered 

 the action of the heart slow, and if the galvanization were 

 sufficiently powerful, arrested the heart, which remained 

 flaccid and in diastole for a certain time while the galvaniza- 

 tion was continued. 1 This fact has since been confirmed by 

 numerous experimenters, whose observations, however, will 

 not be cited in detail, except as they have developed new 

 and important phenomena. 



TVhile there is no difference of opinion among physiolo- 

 gists with regard to the stoppage of the heart by power- 

 ful galvanization, it is stated by some that a very feeble 

 current passed through the peripheral ends of the divided 

 nerves quickens the heart's action ; but it is admitted by all 

 that it is very difficult to regulate the intensity of the cur- 



1 \VEBER, in WAGXER, Handworterbuch der Physiologie, Braunschweig, 1846, 

 Bd. iii., Zweite Abtheilung, S. 42, et seq. 



