PHYSIOLOGICAL REACTIONS 425 



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. 



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 10 c.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- 

 hibition by stimulating the peripheral end of the vagus. In this instance 

 there are no reflexes to complicate the experiment, so that the fall in blood 

 pressure is a direct cardiac effect. Stimulate the central end of the vagus 

 which produces a fall of blood pressure through the vaso-motor system. 

 There should be a normal period of at least ten minutes following each ex- 

 periment to allow the secretion of the kidney to return to the normal. 



Expose the splanchnic nerves at the point where they pass beneath the 

 diaphragm into the abdominal cavity. Adjust a pair of shielded electrodes, 

 close the cavity, and, when the animal has returned to the normal uniform 

 rate of secretion and of blood pressure, stimulate the splanchnic nerves. 

 The splanchnics contain vaso-constrictor nerves for the kidney. The on- 

 kometer experiment should, therefore, demonstrate a sharp decrease in the 

 volume of the organ, while the blood pressure is only slightly changed. The 



