1913.] Expei'iments on the Kidneys of the Frog. 359 



•to the kidneys varies directly with the perfusion rate, a slow perfusion leads 

 to an inadequate oxygen supply to the glomeruli or tubules. 



The amount of fluid escaping from the renal veins on an arterial perfusion 

 alone varied from 20 to 60 c.c. per hour in different experiments ; an average 

 rate was about 30 c.c. per hour. On a venous perfusion alone the rate of 

 perfusion was more constant and averaged 60-70 c.c. per hour. 



Flow of Urhw. — The amount of urine obtained from the normal kidneys 

 •on an arterial perfusion alone varies directly with the rate of perfusion, and 

 under favourable circumstances as much as 1*5 c.c. may be obtained in less 

 than an hour. The concentration of the urine is almost always notably less 

 •than that of the perfusing fluid when the latter is hypotonic Einger's 

 solution ; if the kidneys are perfused with normal Einger's solution the 

 urine may be isotonic with, but is usually hypotonic to, the perfusing fluid. 



The urine obtained on a simultaneous arterial and venous perfusion does 

 not, so far as we could determine, differ in amount from that obtained on an 

 arterial perfusion alone ; a simultaneous arterial and venous perfusion, 

 however, seems to be more conducive to the formation of a very dilute urine 

 than is arterial perfusion alone. 



Table I. — Urine from Living and Dead Kidneys. 



Experiment. 



Concentration. 



• 



Perfusing fluid. 



Urine from normal 

 kidneys. 



Urine from dead 

 kidneys. 



1 

 2 

 3 

 4 

 5 

 6 

 7 



-59 per cent. NaCl 



-57 „ 



0-55 



O -53 



O "42 



O -72 



'83 



per cent. per cent. 

 (a) 0-42 (i) 0-46 

 (a) 0-40 (6) 0-38 

 (a) 0-33 (*) 0-40 



0-25 



0-30 



(a) 0-55 (b) 0-49 

 (a) -73 (b) -68 



per cent. per cent. 

 0-40 



(a) 0-83 (i) 0-83 



The letters (a) and (J) refer to successive samples of urine. 



In Experiment 7 the perfusing fluid contained 0*1 per cent. l^SO* ; in 

 the others the perfusing fluid was simply normal or hypotonic Einger's 

 solution. 



On a venous perfusion alone no urine was secreted with any of the 

 perfusing fluids used. In some of these experiments the arterial circulation 

 was excluded by tying the aortic bulb at the outset and allowing the 

 glomeruli to become infarcted ; in others, the glomeruli had previously been 

 perfused with Einger's solution and the arterial perfusion shut off. 



% 



