HAEMODYNAMICS. 83 



Repeat with the opposite vagus. 



Repeat the experiment using varying strengths of stimuli. 



Explain the results. 



5. DEMONSTRATE THE EFFECT OF VARYING THE PERIPHERAL 

 RESISTANCE ON THE BLOOD PRESSURE; STIMULATION OF SPLANCH- 

 NIC NERVE. Make an incision along the left costal margin starting 

 about 1J inches from the linea alba. After stopping all hemorr- 

 hage,* open the peritoneum and make out the suprarenal capsule 

 lying over a transversely coursing vein. Just outside the suprare- 

 nal and above the vein expose the greater splanchnic nerve by 

 blunt dissection. Tie a ligature loosely around the nerve and lay 

 this on electrodes. While recording a normal tracing of the blood 

 pressure stimulate the nerve (Fig. 24). In taking this tracing all 

 details are to be followed as in par. 4. 



Explain the result. 



The splanchnic nerve is difficult to find unless the abdominal 

 viscera, with the exception of the left kidney, are well retracted 

 to the right. This is to be done by the assistant operator, who, 

 standing on the right of the animal, covers the viscera with cloths 

 wrung out with warm 0.9% NaCl solution, places the left hand 

 with fingers extended over the cloth, and then with the finger tips 

 just touching the posterior wall of the abdomen, pulls the viscera 

 towards the right. With the right hand this operator also pulls 

 down the kidney on the left side. By these procedures the suprare- 

 nal capsule is easily brought into view, and the operator isolates 

 the splanchnic nerve by blunt dissection in the region just above 

 the capsule. 



It is often simpler to find the splanchnic nerve on the right side. 

 In this case, after retraction of the viscera by the procedure de- 

 scribed above, but towards the left side, the right kidney is exposed, 

 and the vein, connecting the abdominal muscles with the adrenal vein, 

 is ligated in two places and cut between the ligatures. The 

 splanchnic nerve is then brought into view by little dissection. 



*The haemorrhage occurs mostly when the muscles are being cut. To arrest it 

 firmly sponge the wound with surgical gauze, locate the bleeding points, catch 

 them in the points of artery forceps (haemostats) and while an assistant gently 

 elevates the point of the forceps, tie a ligature around the tissue caught in them. 

 For venous and capillary oozing, pressure with a piece of gauze wrung out in hot 

 water is usually sufficient. 



