118 DR RUTHERFORD ON THE INFLUENCE OF THE VAGUS 



the pulse in this case took place when no signs of excitement were exhibited 

 by the animal, it therefore seemed to indicate that the right vagus, at any rate, 

 contains efferent cardio-motor nerves""" which are not paralysed by atropia 

 sulphate. The following experiment led me to abandon this idea : — 



Experiment XVIII. — In a rabbit I divided the trunk of the left vagus in 

 the neck, dissected down upon the subclavian artery, and divided the inferior 

 cardiac branch of the right vagus. I then severed the trunk of the vagus on 

 the right side of the neck and irritated its lower end with an induced current 

 (secondary coil 80 mm. from primary coil. One Daniell). The heart's action 

 was accelerated. Before stimulation the heart gives 92 beats in 20" — during 

 stimulation the number rose to 100. On repetition of the above a similar result 

 was obtained. The acceleration in this case could not possibly be due to the 

 action of any motor nerves contained in the inferior cardiac branch of the vagus, 

 for that branch had been divided on the same side as that on which the trunk 

 of the vagus was irritated. I, therefore, concluded that in this and in the pre- 

 ceding experiment, the acceleration of the heart's action was probably due to a 

 reflex excitement of the heart resulting from spasm of the laryngeal and 

 oesophageal muscles, as well as the greatly increased movement of the stomach 

 and intestines which follows powerful stimulation of the lower end of the vagus. 



I have, therefore, entirely failed to find any evidence to the effect that the 

 inferior cardiac branch of the vagus contains any cardio-motor fibres in addition 

 to those which are cardio-inhibitory in their action. 



Effect upon the Vascular System of Section of the Vagi in the Neck. 



It is well known that division of both vagi in the cervical region is — in the 

 case of mammals at any rate — usually followed by accelerated cardiac action 

 and increase of the arterial blood-pressure. 



(a.) Cause of the accelerated Cardiac Action. 



REiDt ascribed it to "the struggles and terror of the animal produced by 

 division of the nerves." Undoubtedly this is to some extent true, but accelera- 

 tion of the heart may be observed after division of the vagi during complete 

 narcotism produced by opium. Brown- Sequard} thought that the excitement 

 of the heart is due to accumulation of carbonic acid in the blood • — it being well 

 known that division of the vagi is usually followed by a slower rate of respira- 



* Since the above was read I have experimented still further with regard to this point. The 

 experiments which I have performed on rabbits and cats have convinced me thoroughly that the vagus 

 does not contain " accelerator" fibres for the heart, and that any acceleration of the heart which may 

 be observed when the lower end of the vagus is stimulated after atropia-poisoning is not due to a direct 

 action of the vagus upon the heart. 



f Physiological Researches, 1848, p. 132. 



| Jl. de la Physiologie, v. p. 656. 



