222 -ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY 



The injection of so large a quantity of solvent is prone to produce a 

 material rise in the blood-pressure, thereby increasing the filtration 

 pressure. For this reason the diuretic effect of sodium chlorid is fre- 

 quently referred to this cause, in combination with hydremia and 

 osmotic changes, and not to a direct stimulating action upon the renal 

 cells. 



5. Effect of Changes in Blood-pressure. When an active secretion 

 has been produced, stimulate the vagus nerve, thereby evoking a 

 material reduction in the general blood-pressure. While the secretion 

 of urine is then greatly lessened, note that the flow does not return to 

 normal until a considerable time after the cessation of the stimulation. 

 This fact tends to show that while the blood-pressure is an important 

 factor in the production of urine, the secreting cells are not dominated 

 by pressure alone. 



Dilute a 1 : 1000 solution of adrenalin sufficiently to cause a moder- 

 ate rise in blood-pressure (2 c.c. of the solution to 20 c.c. of saline). 

 Register the flow of urine. Inject a small quantity of the aforesaid 



FIG. 123. EFFECT OF STIMULATION OF THE VAGUS NERVE UPON THE SECRETION OF 



URINE. 



solution of adrenalin in the external jugular vein. Note that the flow 

 of urine is greatly lessened thereby in spite of the high blood-pressure. 

 This discrepancy is easily explained, because the adrenalin constricts 

 the blood-vessels of the kidney, and gives rise to a lessened vascularity 

 of this organ and lessened secretory power of its cells. 



6. Rapidity of Elimination. Prepare a saturated solution of indigo- 

 carmin. Inject 5 c.c. of this solution in the external jugular vein, not- 

 ing the moment of the injection. Again determine the time when this 

 pigment appears in the urine. Kill the animal by an overdose of ether. 



7. Dissection of the Region of the Kidney. Identify the suprarenal 

 bodies on each side. Carefully remove the left organ and expose the 

 suprarenal plexus, greater and lesser splanchnic nerves, and fibers of 

 the renal plexus. 



Open the pelvis of the kidney and study the characteristics of the cut 

 surface of this organ. Identify the papillae, pyramids, medulla, cortex, 

 and capsule. Remove the capsule. Is it closely adherent to the sub- 

 stance of the kidney? 



