122 ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY 



along its right (as you look at it) upper margin. Very carefully search 

 for a small nerve in the fatty tissue of this region pursuing an oblique 

 course upward through the crus of the diaphragm. This is the left 

 greater splanchnic nerve, connecting the thoracic sympathetic system 

 with the solar plexus. Place a loose silk ligature around it and secure 

 it in shielded electrodes. Insulate by means of a narrow piece of rubber 

 membrane and dry cotton. Allow the parts to close in around the 

 electrodes and apply a warm cloth to the abdomen. 



Allow the carotid blood-pressure to be recorded. Stimulate the 

 aforesaid nerve for about ten seconds until you have obtained an appre- 



FIG. 80. SPLANCHNIC RISE IN BLOOD-PRESSURE. 



ciable rise in pressure. Repeat this procedure after an interval. Apply 

 the clip to the artery. Study the character of the tracing so obtained. 



Annotation. The rise in blood-pressure usually consists of two phases. The 

 first is brought about by the vasoconstriction, resulting in the so-called splanchnic 

 organs in consequence of the excitation of this nerve. This rise appears within a 

 few seconds after the onset of the stimulation and finds its origin in a rapid transfer 

 of blood from the abdominal organs into the channels of the general circulatory 

 system. The second rise appears about ten seconds after the first, and is due to the 

 constriction of the blood-vessels of the general system by the adrenin liberated in 

 consequence of the excitation of this nerve. Obviously, only the left adrenal body is 

 involved, because the innervation of these organs by the splanchnic nerve is uni- 

 lateral. 



Record the blood-pressure. Quickly tighten the silk ligature so as 

 to crush this nerve. Observe the gradual fall in pressure which is 



