ELEMENTARY EXPERIMENTAL PHYSIOLOGY 143 



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

 inhibited, and the arterial pressure falls. Complete arrest cannot be 

 obtained in the cat. It is easily obtained in the dog. In the chloro- 

 formed dog with low blood -pressure, vagus excitation, produced by 

 inhalation of concentrated chloroform vapour, may arrest the heart 



FIG. 140. The kymograph. 



for so long a period as to kill the animal. This is one cause of chloro- 

 form syncope in man. 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. 

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

 (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 



