130 



DR RUTHERFORD ON THE INFLUENCE OF THE VAGUS 



by curara, a slight rise in the blood-pressure frequently resulted from the 

 stimulation. Such a result is shown in the following tracing from a rabbit. 



Fig. 3. 



During — Before— 



Stimulation of the Vagus * 



A change similar to the above is, however, by no means the rule even in the 

 same animal. The following tracing shows no change in the blood-pressure 

 during stimulation of the vagus, although it was taken shortly after the fore- 

 going from the same animal, and although the lower end of the same vagus was 

 stimulated by a current of the same strength. 



Fig. 4. 



During — 



Before- 



Stimulation of the Vagus. 



This tracing represents what I always found when the atropised vagus was 

 stimulated in cases where the influence of extraneous movements upon the 

 blood-pressure had been got rid of by means of curara paralysis. We may, 

 therefore, say, that the vagus certainly contains no vasomotor-nerve fibres 

 which act in a centrifugal direction, for if it did, stimulation of the nerve 

 after palsy of its cardio-inhibitory fibres would always raise the blood-pressure 

 whether curara be given or not. 



(b.) Stimulation of the Upper End of the Nerve. 



Already much has been written with regard to the changes in the blood- 

 pressure which result from stimulating the upper end of the vagus after it has 

 been cut across in the cervical region. According to DRESCHFELDt such stimu- 



* In reading tracings taken by such an instrument as Ludwig's Kymograph, it is necessary to 

 remember that the vertical variations in the mercurial column are always the double of what the tracing 

 indicates, because the tracing shows the movements of a column of mercury in a U-shaped tube. 



t Von Bbzold's Untersuchungen, 1867, p. 326. 



