482 



TEXT-BOOK OF PHYSIOLOGY. 



coat of the afferent and efferent vessels. See Fig. 221 and the accompanying 

 explanation. 



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, from 

 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 pressure 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. 



The period of functional activity of the kidney is accompanied by an 

 increase in the volume of blood flowing through it as is evident from an in- 

 spection of the organ. At this time it is enlarged, swollen, and red in color. 



FIG. 222. FIG. 



FIG. 222. 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. 223. ONCOGRAPH. C'. Chamber filled with oil, communicating by T, with T. p. 

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



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 

 of activity the kidney is supplied with a less amount of blood and hence it 

 diminishes in size, becomes pale in color and the blood of the renal vein 

 becomes dark and venous in character. These variations in the volume of 

 the kidney have also been experimentally determined and registered by 

 means of the oncometer and oncograph devised by Roy. 



The oncometer consists of a metallic box (Fig. 222) composed of halves 

 which open and close by means of a hinge. It is connected with a recording 

 apparatus, the oncograph (Fig. 223), 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 withdrawn from the body, is placed within the oncometer.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 the 

 kidney, as well as the tube leading to the chamber of the oncograph, are 

 completely filled. When the tube I is closed, the conditions are such that all 



