82 EXPERIMENTAL PHYSIOLOGY. 



drum, cut first one and then the other vagus between the ligatures. 

 Note the effect produced on the blood pressure (Fig. 27). To 

 signal the moment of cutting, short-circuit the time tracing for a 

 second or two.* 



Allow several inches of tracing to be recorded after both nerves 



have been cut, so as to be able to determine the after effects; then 



tstop the drum and place the peripheral end of one vagus on elec- 



rode s coming from a short circuiting key which is meanwhile 



a b 



FIG. 24. Arterial blood pressure tracing: (a) during moderate stimulation of the peri- 

 pheral end of vagus; (b) during stimulation of splanchnic nerve. 



closed. Record a short piece of normal tracing and then by opening 

 the short-circuiting key, stimulate the vagus with an induced cur- 

 rent that is just bearable on the tip of the tongue and note the 

 effect produced on the blood pressure. Signal the time of stimula- 

 tion as above directed. Demonstrate escapement. 



*By short-circuiting the time marker in this way the seconds cease to be 

 recorded and the break in the otherwise regular time tracing affords a useful 

 signal indicating the moment of cutting or stimulation. 



