A CTION OF THE CARD I A C NER VES. 2 o 3 



But the upholders of the special cardiac nerve centre theory may 

 argue, " You have given away your case ; you acknowledge that the 

 ganglion cells of the heart must be looked upon as precisely of the same 

 character as the ganglia of the sympathetic system ; and seeing that 

 there is evidence that these latter do act as an independent central 

 nervous system, so it must also be with the former." 



Undoubtedly, the efferent nerve cells, both in the heart and in other 

 places, are the trophic centres of the fibres which spring from them, and 

 in so far as the nutrition of the muscle fibre and its condition of well- 

 being is dependent upon the integrity of its efferent nerves, these nerve 

 cells may be considered as nerve centres governing the muscle ; but a 

 central nervous system means more than this, it means essentially a 

 system of nerve cells and fibres connected with both afferent and efferent 

 nerves, by means of which reflex action is able to take place ; and it is 

 because there is no evidence in any part of this vagrant ganglionic 

 system of any connection between afferent and efferent nerves con- 

 stituting a true reflex arc, that I for one am unable to attribute the 

 function of a central nervous system to any part of it. 



The evidence, as far as it goes at present, seems to point directly to 

 the conclusion that the trophic centre of all the afferent visceral nerves 

 is situated in the stationary ganglia of the posterior roots, and that, 

 therefore, all the nerve cells of the vagrant ganglia are efferent ; that, 

 further, as shown by Langley and Anderson, 1 the so-called reflexes from 

 isolated sympathetic ganglia are not true reflexes, but rather actions 

 along branching efferent nerves. All the conditions necessary for a 

 reflex action of this kind are present in the heart, and in all probability 

 the same explanation as that given by Langley and Anderson for the 

 hypogastric reflex holds good for the reflex which I have described in 

 the heart of the tortoise, 2 upon stimulation of the ventricle, when the 

 auricles are cut away from the ventricle, so that the coronary nerve 

 is the only communication left between ventricle and sinus. In such an 

 experiment the sinus and auricles are beating regularly, and the auricular 

 contractions are registered, while the ventricle remains quiescent. Stimu- 

 lation of the coronary nerve near the ventricle, or of the surface of the 

 ventricle in the neighbourhood of the coronary nerve, caused, when- 

 ever I tried it, a slowing of the rate of beat and a diminution in the 

 strength of the auricular contractions ; caused, in fact, the same effect 

 as a weak vagus stimulation. The strength of stimulus to the ven- 

 tricle, which produced this effect, was not necessarily enough to cause 

 a contraction in the quiescent ventricle. It is to be remarked that the 

 effect was always in the direction of inhibition, as must necessarily be 

 the case if the ganglion cells of the heart are efferent vagus cells, and 

 if the effect of the stimulation was not due to an escape of current but 

 to an efferent reflex action of the kind suggested. 



The Nature of the Action of the Cardiac Nerves. 



1. The action of the inhibitory nerves. — As already stated, Weber 

 pointed out that stimulation of the vagus in the frog not only slows the 

 heart, but also weakens the contractions. In the controversies that fol- 

 lowed, this latter fact was largely lost sight of, until, in Ludwig's laboratory 



1 Joum. Physiol., Cambridge and London, 1894, vol. xvi. }>. 410. 



2 Ibid., 1883, vol. iv. p. 92. 



