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PRACTICAL PHYSIOLOGY 



the blood pressure is high. The pressure (after vagus inhibition) for a 

 brief space of time rises to a higher level. 



Fio. 114. Aortic blood pressure. Effect of posture. A, Vertical head up ; B, horizontal ; C. 

 vertical head down ; D, horizontal. (L.H.) 



The electrodes are now transferred to the central end of the vagus. 

 Excitation produces either a slight rise (pressor effect) or a slight fall 



. Aortic pressure. Spinal cord divided in upper dorsal region. Effect of placing 

 vertical head up posture. The heart emptied. On the return to the horizontal 



Fio. 115. 

 animal in vertical 

 posture the circulation was restored. (L.H.) 



(depressor effect) of pressure. The heart rate is reflexedly slowed, and 

 the respiration is stopped with the diaphragm in inspiratory spasm. 



The electrodes are next transferred to the central end of the 

 depressor nerve. On excitation the blood-pressure slowly falls, and 

 remains at a lower level so long as the excitation is maintained. The 

 rhythm of the heart is as a rule unaffected. The second vagus nerve 



