166 



PRACTICAL PHYSIOLOGY 



FIG. 156. The effect of excitation of the peripheral end of the vagus nerve 

 upon the blood pressure in the aorta (top curve) and the vena cava 

 (second curve) of a curarised animal with artificial respiration. Note 

 the inhibition of the heart ; the great fall of aortic and the insignificant 

 rise of vena cava pressure ; the escape of the heart from the vagus 

 action and the after effect on the aortic pressure. 



The time is marked in seconds, and the signal line shows the duration of vagus stimulation. (L.H.) 



FIG. 157. Aortic blood pressure. 



A, Effect of exciting the central end of vagus. The effect was depressor. B, On shifting up 

 the electrodes to a fresh unexposed part of the nerve the effect changed to pressor. The 

 time is marked in seconds. (L.H.) 



2nd stage : Respiration convulsive, less frequent ; blood pressure 

 rising ; heart slow. At the end of the second stage the pupils 



