414 EXCRETION 



Experimental Observations. There are numerous nerves to the 

 kidney, but no proven secretory influence has been shown. The variations 

 in the secretion of urine that follow nervous stimulation are quite satisfactorily 

 explained by the changes in the blood flow. 



The kidney can be placed in an onkometer and its variation in volume 

 measured directly, figures 301 and 302. This volume measurement, when 

 taken with the arterial pressure, gives a very good index of the volume of 

 blood flowing through the kidney. Now when the kidney is inserted in an 

 onkometer and the urine collected from the ureter, it is found in general that 



FIG. 301. Diagram of Roy's Onkometer. a, Represents the kidney enclosed in a 

 metal box, which opens by hinge/; b, the renal vessels and ducts. Surrounding the kidney 

 are two chambers formed by membranes, the edges of which are firmly fixed by being 

 clamped between the outside and inside metal capsules (the latter not represented in the 

 figure), the two being firmly screwed together by screws at h, and on the opposite side. 

 The membranous chamber below is filled with a varying amount of warm oil, according 

 to the size of the kidney experimented with, through the opening then closed with the plug i. 

 After the kidney has been enclosed in the capsule, the membranous chamber above is filled 

 with warm oil through the tube e, which is then closed by a tap (not represented in the 

 diagram); the tube d communicates with a recording apparatus, and any alteration in the 

 volume of the kidney is communicated by the oil in the tube to the chamber d of the Onko- 

 graph, figure 302. 



the greater the pressure and flow of blood the greater the secretion of urine, 

 as w r ould follow if the glomerulus were a filtering mechanism. However, if 

 the renal vein is partially obstructed, even though the blood pressure be in- 

 creased, the amount of urine secreted is sharply decreased. If the vein is 

 completely occluded, the secretion of urine not only ceases for the time but 

 does not immediately begin again when the blood pressure and flow are re- 

 established. The closure of the vein for only one or two minutes is said to 

 stop the flow of urine for as much as forty-five minutes. This short inter- 

 ruption of the circulation is sufficient to bring about other changes in the 



