226 NEKVOUS SYSTEM. 



rent so as to produce this effect. After section of the nerves, 

 the action of the heart is very readily modified by struggles, 

 etc., on the part of the animal under observation ; and, in 

 view of the exceeding nicety of the reported experiments, 

 it cannot be admitted that the heart is capable of being ex- 

 cited to increased rapidity of action, without observations 

 of the most positive character. Such facts are wanting; 

 and furthermore, it has been shown by Dr. Rutherford, in a 

 series of exceedingly exact and satisfactory experiments, that 

 whenever a galvanic current passed through the pneumo- 

 gastrics has any appreciable effect upon the action of the heart, 

 it is to diminish the frequency of its pulsations. 1 Inasmuch 

 as our object is simply to show that, imitating the nervous 

 force by galvanism, the action of the pneumogastrics is in- 

 hibitory, we will not discuss the effects of different currents, 

 and other experiments, which have little relation to the 

 natural action of the nerves, and possess slight interest from 

 a purely physiological point of view. 



The direct action of the pneumogastrics upon the heart 

 is undoubtedly through their motor filaments. All the facts 

 developed by experiments are in accordance with this view. 

 If the nerves be divided in the neck, galvanization of the 

 central ends has no effect upon the heart, the pulsations 

 being arrested only when the peripheral ends are stimulated. 

 This shows that, at least as far as the fibres passing down 

 the neck are concerned, the action is centrifugal and di- 

 rect, not reflex. Another curious fact illustrates the same 

 point very forcibly. It is well known that the woorara- 

 poison completely paralyzes the motor nerves, leaving the 

 muscular irritability and the sensory nerves intact. It has 

 been found that, in animals poisoned with woorara, the action 

 }f the heart being maintained by artificial respiration, gal- 

 vanization of both pneumogastrics has no effect upon its 



1 RUTHERFORD, Influence of the Vagus upon the Vascular System. Journal 

 of Anatomy and Physiology, Cambridge and London, 1869, vol. iii., p. 404, 



