EXCRETION. 



Coincident with the rise and fall of pressure in the glomerular 

 capillaries there is a rise and fall in the rate of urinary flow. Thus 

 it has been found that an increase in the aortic pressure from 127 to 

 142 mm. of mercury, by ligation of the carotid, femoral, and vertebral 

 arteries, increased the rate of urinary flow from 8.7 grams in thirty 

 minutes to 21.2 grams. On the contrary, a decrease in aortic pres- 

 sure below 40 mm. of mercury caused by division of the spinal cord 

 is followed by a total abolition of the urinary flow. These facts 

 serve to indicate the dependence of the secretion on blood-pressure. 



That there is an increase in the volume of the blood flowing 

 through the kidney during its functional activity is apparent from 

 inspection. It is enlarged, swollen, and red in color. The blood in 

 the renal vein is bright red in color and contains more oxygen and 

 less carbon dioxid than venous blood generally. During the intervals 



FIG. 196. ONCOMETER. K. Kidney; the thick line is the metallic capsule, h. 



Hinge. I. Tube for filling apparatus. T. Tube to connect with T,. a, v, u. 



Artery, vein, ureter. (Stirling, after Roy.} 



FIG. 197. ONCOGRAPH. C'. Chamber filled with oil, communicating by T, with 

 T. p. Piston. 1. Writing-lever. (Stirling, after Roy.) 



of activity the kidney diminishes in size, is pale in color and the 

 blood of the renal vein dark and venous in character. These varia- 

 tions in the volume of the kidney have also been experimentally deter- 

 mined and registered by means of the oncometer and oncograph 

 devised by Roy (Figs. 196 and 197). 



The oncometer consists of a metallic box (Fig. 196) composed 

 of halves which open and close by means of a hinge. It is con- 

 nected with a recording apparatus, the oncograph (Fig. 197), through 

 the tube T. The kidney, withdrawn from the body, is placed 

 within the oncometer. Through an opening in the side pass the 

 artery, vein, and ureter. Between the kidney and the wall of 

 the capsule there is placed a thin membrane. Oil is then poured 

 through the side tube I until the space between the capsule and 



