STRUCTURE AND FUNCTION OF THE KIDNEYS. 375 



ever, to the response of the kidney to alterations in the general blood- 

 pressure, it has been further observed that certain substances, when 

 injected into the blood, will also produce an increase in volume of the 

 kidney, and consequent increased flow of urine, without affecting the 

 general blood-pressure such bodies as sodium acetate and other diuret- 

 ics. These observations appear to prove that local dilatation of the 

 renal vessels may be produced by alterations in the blood acting upon a 

 local nervous mechanism, as this happens when all of the renal nerves 

 have been divided. The alterations are not only produced by the addi- 

 tion of drugs, but also by the introduction of comparatively small 

 quantities of water or saline solution. To this alteration of the blood 

 acting upon the renal vessels (either directly or) through a local vaso- 

 motor mechanism, and not to any great alteration in the general blood- 



FIG. 260. Diagram of Roy's Oncometer. a, represents the kidney inclosed in a metal box 

 which opens by hinge/; 6, the renal vessels and duct. Surrounding the kidney are two chambers 

 formed by membranes, the edges of which are firmly fixed by being clamped between the outside 

 metal capsule, and one (not represented in the figure) inside, the two being firmly screwed together 

 by screws at h, and below. 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 inclosed 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 Oncograph, 

 Fig. 261. 



pressure, must we attribute the effects of meals, etc., observed by 

 Roberts. " The renal excretion is increased after meals and diminished 

 during fasting and sleep. The increase began within the first hour 

 after breakfast, and continued during the succeeding two or three 

 hours; then a diminution set in, and continued until an hour or two 

 after dinner. The effect of dinner did not appear until two or three 

 hours after the meal; and it reached its maximum about the fourth 

 hour. From this period the excretion steadily decreased until bed-time. 

 During sleep it sank still lower, and reached its minimum being not 



