164 



PRACTICAL PHYSIOLOGY 



The clip is then removed from the carotid artery and the kymograph 

 started. Note the height of the arterial pressure, the cardiac pulsa- 

 tions, and the respiratory oscillations of arterial pressure. The 

 pulsations are distorted by the momentum of the mercury. 



The inspiratory fall of intra-thoracic pressure aspirates blood 

 into the intra-thoracic veins and thin-walled auricles, and dilates 

 the pulmonary vessels. The descent of the diaphragm expresses 

 blood from the liver and abdominal vessels into the right heart in 



FIG. 154. The kymograph. 



the living animal. Thoracic and abdominal breathing have a 

 contrary effect. Thoracic breathing produces an inspiratory fall 

 of arterial pressure, and abdominal an inspiratory rise. 



Stimulate the peripheral end of the vagus nerve. The heart is 

 inhibited, and the arterial pressure falls. The heart soon escapes 

 from vagus arrest if the blood pressure is high. The pressure 

 (after vagus inhibition) for a brief space of time rises to a higher 

 level. 



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



