448 EXCRETION 



LABORATORY EXPERIMENTS IN EXCRETION. 

 PHYSIOLOGICAL REACTIONS. 



i. The Relation of Blood Flow through the Kidney to the Secre- 

 tion of Urine. Properly to check this experiment one should make three 

 determinations: i, the general blood pressure; 2, the volume of the kid- 

 ney; 3, the amount of urine secreted. Anesthetize a dog and arrange the 

 apparatus for taking the blood pressure as directed in experiment 19. Pre- 

 pare a renal onkometer, see figures 301 and 302, and an onkograph for re- 

 cording the variations in the volume of the kidney. The renal onkometer 

 consists of a double metal box to fit the form of a kidney. The inner halves 

 of this box should be covered so loosely with very thin sheet rubber that the 

 rubber can be fitted into the bottom of the cup without undue tension. The 

 rubber must be sealed to the outer edges of this inner cup with rubber cement 

 and allowed to dry. When it is completely dried the inner cup should be ad- 

 justed to the outer, and the spaces enclosed by the rubber sheet filled with 

 water. Or the onkometer may be closed with parchment and filled with oil 

 as described in experiment 23 on the Circulation. The half of the onkom- 

 eter that comes against the wall of the body cavity of the animal should be 

 completely closed with a stopper before the instrument is adjusted to the 

 kidney. Now adjust the onkometer to the kidney, taking care to place 

 the renal arteries, veins, and ureter in the tube in such a way as not to com- 

 press them. Fill the outer cup with water and connect this cavity by a 

 two-way cannula with the recording onkograph. In practice it is more 

 satisfactory if one introduces between the onkometer and onkograph an over- 

 flow bottle or bulb, adjusted to maintain the constant pressure on the kidney. 

 This direction varies from the usual one in that rubber sheeting instead of 

 parchment is used to cover the inner cup of the onkometer, a method that 

 permits the use of water instead of oil. Recently Jackson has introduced 

 an air onkometer that is simpler to prepare and adjust. The seal is se- 

 cured by wrapping it in folds of omentum after inserting the kidney. An 

 air recorder must of course be used. 



Isolate and insert a small cannula into the ureter. This cannula should 

 be clamped in a stand at a level as little above that of the kidney as possible. 

 The urine secreted may be collected in a loc.c. graduated cylinder and 

 measured at intervals of 5 or 10 minutes. Or, if the outflow is scanty, it may 

 be allowed to drop on a tambour recording apparatus, the rate of dropping 

 being indicative of the rapidity of secretion. 



Determine the normal rate of secretion of a dog under constant anesthesia. 

 The anesthesia should be medium to light, but should be kept very uni- 

 form so as to maintain a strong blood pressure. Note the effect on secre- 

 tion and the corresponding effect on blood pressure and the kidney volume 

 produced by vagus inhibitions. Section the vagus nerves and produce in- 



