132 PRACTICAL PHYSIOLOGY 



pulmonic system lessens the flow of blood into the left heart, and 



Fio. 110. 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.) 



arterial pressure falls. Expiration expresses blood from the pulmonic 

 system into the left heart, and arterial pressure rises. When the rate 



A B 



Fio. 111. 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.) 



of respiration is slow there is time for the increased or diminished 

 entry of blood into the right heart to exert its effect in the latter stage 

 of inspiration and expiration respectively. 



